org.apache.commons.io

## Class FileUtils

- java.lang.Object
- - org.apache.commons.io.FileUtils

    public class FileUtils
    extends Object

General file manipulation utilities.

Facilities are provided in the following areas:

- writing to a file
- reading from a file
- make a directory including parent directories
- copying files and directories
- deleting files and directories
- converting to and from a URL
- listing files and directories by filter and extension
- comparing file content
- file last changed date
- calculating a checksum

Note that a specific charset should be specified whenever possible. Relying on the platform default means that the code is Locale-dependent. Only use the default if the files are known to always use the platform default.

Origin of code: Excalibur, Alexandria, Commons-Utils

### Field Summary

Fields
`static File[]` `EMPTY_FILE_ARRAY` An empty array of type `File`.
`static long` `ONE_EB` The number of bytes in an exabyte.
`static BigInteger` `ONE_EB_BI` The number of bytes in an exabyte.
`static long` `ONE_GB` The number of bytes in a gigabyte.
`static BigInteger` `ONE_GB_BI` The number of bytes in a gigabyte.
`static long` `ONE_KB` The number of bytes in a kilobyte.
`static BigInteger` `ONE_KB_BI` The number of bytes in a kilobyte.
`static long` `ONE_MB` The number of bytes in a megabyte.
`static BigInteger` `ONE_MB_BI` The number of bytes in a megabyte.
`static long` `ONE_PB` The number of bytes in a petabyte.
`static BigInteger` `ONE_PB_BI` The number of bytes in a petabyte.
`static long` `ONE_TB` The number of bytes in a terabyte.
`static BigInteger` `ONE_TB_BI` The number of bytes in a terabyte.
`static BigInteger` `ONE_YB` The number of bytes in a yottabyte.
`static BigInteger` `ONE_ZB` The number of bytes in a zettabyte.

### Constructor Summary

Constructors
Constructor and Description
`FileUtils()` Instances should NOT be constructed in standard programming.

### Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
`static String` `byteCountToDisplaySize(BigInteger size)` Returns a human-readable version of the file size, where the input represents a specific number of bytes.
`static String` `byteCountToDisplaySize(long size)` Returns a human-readable version of the file size, where the input represents a specific number of bytes.
`static Checksum` `checksum(File file, Checksum checksum)` Computes the checksum of a file using the specified checksum object.
`static long` `checksumCRC32(File file)` Computes the checksum of a file using the CRC32 checksum routine.
`static void` `cleanDirectory(File directory)` Cleans a directory without deleting it.
`static boolean` `contentEquals(File file1, File file2)` Compares the contents of two files to determine if they are equal or not.
`static boolean` `contentEqualsIgnoreEOL(File file1, File file2, String charsetName)` Compares the contents of two files to determine if they are equal or not.
`static File[]` `convertFileCollectionToFileArray(Collection<File> files)` Converts a Collection containing java.io.File instanced into array representation.
`static void` `copyDirectory(File srcDir, File destDir)` Copies a whole directory to a new location preserving the file dates.
`static void` `copyDirectory(File srcDir, File destDir, boolean preserveFileDate)` Copies a whole directory to a new location.
`static void` `copyDirectory(File srcDir, File destDir, FileFilter filter)` Copies a filtered directory to a new location preserving the file dates.
`static void` `copyDirectory(File srcDir, File destDir, FileFilter filter, boolean preserveFileDate)` Copies a filtered directory to a new location.
`static void` `copyDirectoryToDirectory(File srcDir, File destDir)` Copies a directory to within another directory preserving the file dates.
`static void` `copyFile(File srcFile, File destFile)` Copies a file to a new location preserving the file date.
`static void` `copyFile(File srcFile, File destFile, boolean preserveFileDate)` Copies a file to a new location.
`static long` `copyFile(File input, OutputStream output)` Copy bytes from a `File` to an `OutputStream`.
`static void` `copyFileToDirectory(File srcFile, File destDir)` Copies a file to a directory preserving the file date.
`static void` `copyFileToDirectory(File srcFile, File destDir, boolean preserveFileDate)` Copies a file to a directory optionally preserving the file date.
`static void` `copyInputStreamToFile(InputStream source, File destination)` Copies bytes from an `InputStream` `source` to a file `destination`.
`static void` `copyToDirectory(File src, File destDir)` Copies a file or directory to within another directory preserving the file dates.
`static void` `copyToDirectory(Iterable<File> srcs, File destDir)` Copies a files to a directory preserving each file's date.
`static void` `copyToFile(InputStream source, File destination)` Copies bytes from an `InputStream` `source` to a file `destination`.
`static void` `copyURLToFile(URL source, File destination)` Copies bytes from the URL `source` to a file `destination`.
`static void` `copyURLToFile(URL source, File destination, int connectionTimeout, int readTimeout)` Copies bytes from the URL `source` to a file `destination`.
`static void` `deleteDirectory(File directory)` Deletes a directory recursively.
`static boolean` `deleteQuietly(File file)` Deletes a file, never throwing an exception.
`static boolean` `directoryContains(File directory, File child)` Determines whether the `parent` directory contains the `child` element (a file or directory).
`static void` `forceDelete(File file)` Deletes a file.
`static void` `forceDeleteOnExit(File file)` Schedules a file to be deleted when JVM exits.
`static void` `forceMkdir(File directory)` Makes a directory, including any necessary but nonexistent parent directories.
`static void` `forceMkdirParent(File file)` Makes any necessary but nonexistent parent directories for a given File.
`static File` `getFile(File directory, String... names)` Construct a file from the set of name elements.
`static File` `getFile(String... names)` Construct a file from the set of name elements.
`static File` `getTempDirectory()` Returns a `File` representing the system temporary directory.
`static String` `getTempDirectoryPath()` Returns the path to the system temporary directory.
`static File` `getUserDirectory()` Returns a `File` representing the user's home directory.
`static String` `getUserDirectoryPath()` Returns the path to the user's home directory.
`static boolean` `isFileNewer(File file, Date date)` Tests if the specified `File` is newer than the specified `Date`.
`static boolean` `isFileNewer(File file, File reference)` Tests if the specified `File` is newer than the reference `File`.
`static boolean` `isFileNewer(File file, long timeMillis)` Tests if the specified `File` is newer than the specified time reference.
`static boolean` `isFileOlder(File file, Date date)` Tests if the specified `File` is older than the specified `Date`.
`static boolean` `isFileOlder(File file, File reference)` Tests if the specified `File` is older than the reference `File`.
`static boolean` `isFileOlder(File file, long timeMillis)` Tests if the specified `File` is older than the specified time reference.
`static boolean` `isSymlink(File file)` Determines whether the specified file is a Symbolic Link rather than an actual file.
`static Iterator<File>` `iterateFiles(File directory, IOFileFilter fileFilter, IOFileFilter dirFilter)` Allows iteration over the files in given directory (and optionally its subdirectories).
`static Iterator<File>` `iterateFiles(File directory, String[] extensions, boolean recursive)` Allows iteration over the files in a given directory (and optionally its subdirectories) which match an array of extensions.
`static Iterator<File>` `iterateFilesAndDirs(File directory, IOFileFilter fileFilter, IOFileFilter dirFilter)` Allows iteration over the files in given directory (and optionally its subdirectories).
`static LineIterator` `lineIterator(File file)` Returns an Iterator for the lines in a `File` using the default encoding for the VM.
`static LineIterator` `lineIterator(File file, String encoding)` Returns an Iterator for the lines in a `File`.
`static Collection<File>` `listFiles(File directory, IOFileFilter fileFilter, IOFileFilter dirFilter)` Finds files within a given directory (and optionally its subdirectories).
`static Collection<File>` `listFiles(File directory, String[] extensions, boolean recursive)` Finds files within a given directory (and optionally its subdirectories) which match an array of extensions.
`static Collection<File>` `listFilesAndDirs(File directory, IOFileFilter fileFilter, IOFileFilter dirFilter)` Finds files within a given directory (and optionally its subdirectories).
`static void` `moveDirectory(File srcDir, File destDir)` Moves a directory.
`static void` `moveDirectoryToDirectory(File src, File destDir, boolean createDestDir)` Moves a directory to another directory.
`static void` `moveFile(File srcFile, File destFile)` Moves a file.
`static void` `moveFileToDirectory(File srcFile, File destDir, boolean createDestDir)` Moves a file to a directory.
`static void` `moveToDirectory(File src, File destDir, boolean createDestDir)` Moves a file or directory to the destination directory.
`static FileInputStream` `openInputStream(File file)` Opens a `FileInputStream` for the specified file, providing better error messages than simply calling `new FileInputStream(file)`.
`static FileOutputStream` `openOutputStream(File file)` Opens a `FileOutputStream` for the specified file, checking and creating the parent directory if it does not exist.
`static FileOutputStream` `openOutputStream(File file, boolean append)` Opens a `FileOutputStream` for the specified file, checking and creating the parent directory if it does not exist.
`static byte[]` `readFileToByteArray(File file)` Reads the contents of a file into a byte array.
`static String` `readFileToString(File file)` Deprecated. 2.5 use `readFileToString(File, Charset)` instead (and specify the appropriate encoding)
`static String` `readFileToString(File file, Charset encoding)` Reads the contents of a file into a String.
`static String` `readFileToString(File file, String encoding)` Reads the contents of a file into a String.
`static List<String>` `readLines(File file)` Deprecated. 2.5 use `readLines(File, Charset)` instead (and specify the appropriate encoding)
`static List<String>` `readLines(File file, Charset encoding)` Reads the contents of a file line by line to a List of Strings.
`static List<String>` `readLines(File file, String encoding)` Reads the contents of a file line by line to a List of Strings.
`static long` `sizeOf(File file)` Returns the size of the specified file or directory.
`static BigInteger` `sizeOfAsBigInteger(File file)` Returns the size of the specified file or directory.
`static long` `sizeOfDirectory(File directory)` Counts the size of a directory recursively (sum of the length of all files).
`static BigInteger` `sizeOfDirectoryAsBigInteger(File directory)` Counts the size of a directory recursively (sum of the length of all files).
`static File` `toFile(URL url)` Convert from a `URL` to a `File`.
`static File[]` `toFiles(URL[] urls)` Converts each of an array of `URL` to a `File`.
`static void` `touch(File file)` Implements the same behaviour as the "touch" utility on Unix.
`static URL[]` `toURLs(File[] files)` Converts each of an array of `File` to a `URL`.
`static boolean` `waitFor(File file, int seconds)` Waits for NFS to propagate a file creation, imposing a timeout.
`static void` `write(File file, CharSequence data)` Deprecated. 2.5 use `write(File, CharSequence, Charset)` instead (and specify the appropriate encoding)
`static void` `write(File file, CharSequence data, boolean append)` Deprecated. 2.5 use `write(File, CharSequence, Charset, boolean)` instead (and specify the appropriate encoding)
`static void` `write(File file, CharSequence data, Charset encoding)` Writes a CharSequence to a file creating the file if it does not exist.
`static void` `write(File file, CharSequence data, Charset encoding, boolean append)` Writes a CharSequence to a file creating the file if it does not exist.
`static void` `write(File file, CharSequence data, String encoding)` Writes a CharSequence to a file creating the file if it does not exist.
`static void` `write(File file, CharSequence data, String encoding, boolean append)` Writes a CharSequence to a file creating the file if it does not exist.
`static void` `writeByteArrayToFile(File file, byte[] data)` Writes a byte array to a file creating the file if it does not exist.
`static void` `writeByteArrayToFile(File file, byte[] data, boolean append)` Writes a byte array to a file creating the file if it does not exist.
`static void` `writeByteArrayToFile(File file, byte[] data, int off, int len)` Writes `len` bytes from the specified byte array starting at offset `off` to a file, creating the file if it does not exist.
`static void` `writeByteArrayToFile(File file, byte[] data, int off, int len, boolean append)` Writes `len` bytes from the specified byte array starting at offset `off` to a file, creating the file if it does not exist.
`static void` `writeLines(File file, Collection<?> lines)` Writes the `toString()` value of each item in a collection to the specified `File` line by line.
`static void` `writeLines(File file, Collection<?> lines, boolean append)` Writes the `toString()` value of each item in a collection to the specified `File` line by line.
`static void` `writeLines(File file, Collection<?> lines, String lineEnding)` Writes the `toString()` value of each item in a collection to the specified `File` line by line.
`static void` `writeLines(File file, Collection<?> lines, String lineEnding, boolean append)` Writes the `toString()` value of each item in a collection to the specified `File` line by line.
`static void` `writeLines(File file, String encoding, Collection<?> lines)` Writes the `toString()` value of each item in a collection to the specified `File` line by line.
`static void` `writeLines(File file, String encoding, Collection<?> lines, boolean append)` Writes the `toString()` value of each item in a collection to the specified `File` line by line, optionally appending.
`static void` `writeLines(File file, String encoding, Collection<?> lines, String lineEnding)` Writes the `toString()` value of each item in a collection to the specified `File` line by line.
`static void` `writeLines(File file, String encoding, Collection<?> lines, String lineEnding, boolean append)` Writes the `toString()` value of each item in a collection to the specified `File` line by line.
`static void` `writeStringToFile(File file, String data)` Deprecated. 2.5 use `writeStringToFile(File, String, Charset)` instead (and specify the appropriate encoding)
`static void` `writeStringToFile(File file, String data, boolean append)` Deprecated. 2.5 use `writeStringToFile(File, String, Charset, boolean)` instead (and specify the appropriate encoding)
`static void` `writeStringToFile(File file, String data, Charset encoding)` Writes a String to a file creating the file if it does not exist.
`static void` `writeStringToFile(File file, String data, Charset encoding, boolean append)` Writes a String to a file creating the file if it does not exist.
`static void` `writeStringToFile(File file, String data, String encoding)` Writes a String to a file creating the file if it does not exist.
`static void` `writeStringToFile(File file, String data, String encoding, boolean append)` Writes a String to a file creating the file if it does not exist.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

### Field Detail

#### ONE_KB

    public static final long ONE_KB

The number of bytes in a kilobyte.

See Also:
  Constant Field Values

#### ONE_KB_BI

    public static final BigInteger ONE_KB_BI

The number of bytes in a kilobyte.

Since:
  2.4

#### ONE_MB

    public static final long ONE_MB

The number of bytes in a megabyte.

See Also:
  Constant Field Values

#### ONE_MB_BI

    public static final BigInteger ONE_MB_BI

The number of bytes in a megabyte.

Since:
  2.4

#### ONE_GB

    public static final long ONE_GB

The number of bytes in a gigabyte.

See Also:
  Constant Field Values

#### ONE_GB_BI

    public static final BigInteger ONE_GB_BI

The number of bytes in a gigabyte.

Since:
  2.4

#### ONE_TB

    public static final long ONE_TB

The number of bytes in a terabyte.

See Also:
  Constant Field Values

#### ONE_TB_BI

    public static final BigInteger ONE_TB_BI

The number of bytes in a terabyte.

Since:
  2.4

#### ONE_PB

    public static final long ONE_PB

The number of bytes in a petabyte.

See Also:
  Constant Field Values

#### ONE_PB_BI

    public static final BigInteger ONE_PB_BI

The number of bytes in a petabyte.

Since:
  2.4

#### ONE_EB

    public static final long ONE_EB

The number of bytes in an exabyte.

See Also:
  Constant Field Values

#### ONE_EB_BI

    public static final BigInteger ONE_EB_BI

The number of bytes in an exabyte.

Since:
  2.4

#### ONE_ZB

    public static final BigInteger ONE_ZB

The number of bytes in a zettabyte.

#### ONE_YB

    public static final BigInteger ONE_YB

The number of bytes in a yottabyte.

#### EMPTY_FILE_ARRAY

    public static final File[] EMPTY_FILE_ARRAY

An empty array of type `File`.

### Constructor Detail

#### FileUtils

    public FileUtils()

Instances should NOT be constructed in standard programming.

### Method Detail

#### getFile

    public static File getFile(File directory,
                               String... names)

Construct a file from the set of name elements.

Parameters:
  `directory` - the parent directory
  `names` - the name elements
Returns:
  the file
Since:
  2.1

#### getFile

    public static File getFile(String... names)

Construct a file from the set of name elements.

Parameters:
  `names` - the name elements
Returns:
  the file
Since:
  2.1

#### getTempDirectoryPath

    public static String getTempDirectoryPath()

Returns the path to the system temporary directory.

Returns:
  the path to the system temporary directory.
Since:
  2.0

#### getTempDirectory

    public static File getTempDirectory()

Returns a `File` representing the system temporary directory.

Returns:
  the system temporary directory.
Since:
  2.0

#### getUserDirectoryPath

    public static String getUserDirectoryPath()

Returns the path to the user's home directory.

Returns:
  the path to the user's home directory.
Since:
  2.0

#### getUserDirectory

    public static File getUserDirectory()

Returns a `File` representing the user's home directory.

Returns:
  the user's home directory.
Since:
  2.0

#### openInputStream

    public static FileInputStream openInputStream(File file)
                                           throws IOException

Opens a `FileInputStream` for the specified file, providing better error messages than simply calling `new FileInputStream(file)`.

At the end of the method either the stream will be successfully opened, or an exception will have been thrown.

An exception is thrown if the file does not exist. An exception is thrown if the file object exists but is a directory. An exception is thrown if the file exists but cannot be read.

Parameters:
  `file` - the file to open for input, must not be `null`
Returns:
  a new `FileInputStream` for the specified file
Throws:
  `FileNotFoundException` - if the file does not exist
  `IOException` - if the file object is a directory
  `IOException` - if the file cannot be read
Since:
  1.3

#### openOutputStream

    public static FileOutputStream openOutputStream(File file)
                                             throws IOException

Opens a `FileOutputStream` for the specified file, checking and creating the parent directory if it does not exist.

At the end of the method either the stream will be successfully opened, or an exception will have been thrown.

The parent directory will be created if it does not exist. The file will be created if it does not exist. An exception is thrown if the file object exists but is a directory. An exception is thrown if the file exists but cannot be written to. An exception is thrown if the parent directory cannot be created.

Parameters:
  `file` - the file to open for output, must not be `null`
Returns:
  a new `FileOutputStream` for the specified file
Throws:
  `IOException` - if the file object is a directory
  `IOException` - if the file cannot be written to
  `IOException` - if a parent directory needs creating but that fails
Since:
  1.3

#### openOutputStream

    public static FileOutputStream openOutputStream(File file,
                                                    boolean append)
                                             throws IOException

Opens a `FileOutputStream` for the specified file, checking and creating the parent directory if it does not exist.

At the end of the method either the stream will be successfully opened, or an exception will have been thrown.

The parent directory will be created if it does not exist. The file will be created if it does not exist. An exception is thrown if the file object exists but is a directory. An exception is thrown if the file exists but cannot be written to. An exception is thrown if the parent directory cannot be created.

Parameters:
  `file` - the file to open for output, must not be `null`
  `append` - if `true`, then bytes will be added to the end of the file rather than overwriting
Returns:
  a new `FileOutputStream` for the specified file
Throws:
  `IOException` - if the file object is a directory
  `IOException` - if the file cannot be written to
  `IOException` - if a parent directory needs creating but that fails
Since:
  2.1

#### byteCountToDisplaySize

    public static String byteCountToDisplaySize(BigInteger size)

Returns a human-readable version of the file size, where the input represents a specific number of bytes.

If the size is over 1GB, the size is returned as the number of whole GB, i.e. the size is rounded down to the nearest GB boundary.

Similarly for the 1MB and 1KB boundaries.

Parameters:
  `size` - the number of bytes
Returns:
  a human-readable display value (includes units - EB, PB, TB, GB, MB, KB or bytes)
Since:
  2.4
See Also:
  IO-226 - should the rounding be changed?

#### byteCountToDisplaySize

    public static String byteCountToDisplaySize(long size)

Returns a human-readable version of the file size, where the input represents a specific number of bytes.

If the size is over 1GB, the size is returned as the number of whole GB, i.e. the size is rounded down to the nearest GB boundary.

Similarly for the 1MB and 1KB boundaries.

Parameters:
  `size` - the number of bytes
Returns:
  a human-readable display value (includes units - EB, PB, TB, GB, MB, KB or bytes)
See Also:
  IO-226 - should the rounding be changed?

#### touch

    public static void touch(File file)
                      throws IOException

Implements the same behaviour as the "touch" utility on Unix. It creates a new file with size 0 or, if the file exists already, it is opened and closed without modifying it, but updating the file date and time.

NOTE: As from v1.3, this method throws an IOException if the last modified date of the file cannot be set. Also, as from v1.3 this method creates parent directories if they do not exist.

Parameters:
  `file` - the File to touch
Throws:
  `IOException` - If an I/O problem occurs

#### convertFileCollectionToFileArray

    public static File[] convertFileCollectionToFileArray(Collection<File> files)

Converts a Collection containing java.io.File instanced into array representation. This is to account for the difference between File.listFiles() and FileUtils.listFiles().

Parameters:
  `files` - a Collection containing java.io.File instances
Returns:
  an array of java.io.File

#### listFiles

    public static Collection<File> listFiles(File directory,
                                             IOFileFilter fileFilter,
                                             IOFileFilter dirFilter)

Finds files within a given directory (and optionally its subdirectories). All files found are filtered by an IOFileFilter.

If your search should recurse into subdirectories you can pass in an IOFileFilter for directories. You don't need to bind a DirectoryFileFilter (via logical AND) to this filter. This method does that for you.

An example: If you want to search through all directories called "temp" you pass in `FileFilterUtils.NameFileFilter("temp")`

Another common usage of this method is find files in a directory tree but ignoring the directories generated CVS. You can simply pass in `FileFilterUtils.makeCVSAware(null)`.

Parameters:
  `directory` - the directory to search in
  `fileFilter` - filter to apply when finding files. Must not be `null`, use `TrueFileFilter.INSTANCE` to match all files in selected directories.
  `dirFilter` - optional filter to apply when finding subdirectories. If this parameter is `null`, subdirectories will not be included in the search. Use `TrueFileFilter.INSTANCE` to match all directories.
Returns:
  a collection of java.io.File with the matching files
See Also:
  `FileFilterUtils`, `NameFileFilter`

#### listFilesAndDirs

    public static Collection<File> listFilesAndDirs(File directory,
                                                    IOFileFilter fileFilter,
                                                    IOFileFilter dirFilter)

Finds files within a given directory (and optionally its subdirectories). All files found are filtered by an IOFileFilter.

The resulting collection includes the starting directory and any subdirectories that match the directory filter.

Parameters:
  `directory` - the directory to search in
  `fileFilter` - filter to apply when finding files.
  `dirFilter` - optional filter to apply when finding subdirectories. If this parameter is `null`, subdirectories will not be included in the search. Use TrueFileFilter.INSTANCE to match all directories.
Returns:
  a collection of java.io.File with the matching files
Since:
  2.2
See Also:
  `listFiles(java.io.File, org.apache.commons.io.filefilter.IOFileFilter, org.apache.commons.io.filefilter.IOFileFilter)`, `FileFilterUtils`, `NameFileFilter`

#### iterateFiles

    public static Iterator<File> iterateFiles(File directory,
                                              IOFileFilter fileFilter,
                                              IOFileFilter dirFilter)

Allows iteration over the files in given directory (and optionally its subdirectories).

All files found are filtered by an IOFileFilter. This method is based on `listFiles(File, IOFileFilter, IOFileFilter)`, which supports Iterable ('foreach' loop).

Parameters:
  `directory` - the directory to search in
  `fileFilter` - filter to apply when finding files.
  `dirFilter` - optional filter to apply when finding subdirectories. If this parameter is `null`, subdirectories will not be included in the search. Use TrueFileFilter.INSTANCE to match all directories.
Returns:
  an iterator of java.io.File for the matching files
Since:
  1.2
See Also:
  `FileFilterUtils`, `NameFileFilter`

#### iterateFilesAndDirs

    public static Iterator<File> iterateFilesAndDirs(File directory,
                                                     IOFileFilter fileFilter,
                                                     IOFileFilter dirFilter)

Allows iteration over the files in given directory (and optionally its subdirectories).

All files found are filtered by an IOFileFilter. This method is based on `listFilesAndDirs(File, IOFileFilter, IOFileFilter)`, which supports Iterable ('foreach' loop).

The resulting iterator includes the subdirectories themselves.

Parameters:
  `directory` - the directory to search in
  `fileFilter` - filter to apply when finding files.
  `dirFilter` - optional filter to apply when finding subdirectories. If this parameter is `null`, subdirectories will not be included in the search. Use TrueFileFilter.INSTANCE to match all directories.
Returns:
  an iterator of java.io.File for the matching files
Since:
  2.2
See Also:
  `FileFilterUtils`, `NameFileFilter`

#### listFiles

    public static Collection<File> listFiles(File directory,
                                             String[] extensions,
                                             boolean recursive)

Finds files within a given directory (and optionally its subdirectories) which match an array of extensions.

Parameters:
  `directory` - the directory to search in
  `extensions` - an array of extensions, ex. {"java","xml"}. If this parameter is `null`, all files are returned.
  `recursive` - if true all subdirectories are searched as well
Returns:
  a collection of java.io.File with the matching files

#### iterateFiles

    public static Iterator<File> iterateFiles(File directory,
                                              String[] extensions,
                                              boolean recursive)

Allows iteration over the files in a given directory (and optionally its subdirectories) which match an array of extensions. This method is based on `listFiles(File, String[], boolean)`, which supports Iterable ('foreach' loop).

Parameters:
  `directory` - the directory to search in
  `extensions` - an array of extensions, ex. {"java","xml"}. If this parameter is `null`, all files are returned.
  `recursive` - if true all subdirectories are searched as well
Returns:
  an iterator of java.io.File with the matching files
Since:
  1.2

#### contentEquals

    public static boolean contentEquals(File file1,
                                        File file2)
                                 throws IOException

Compares the contents of two files to determine if they are equal or not.

This method checks to see if the two files are different lengths or if they point to the same file, before resorting to byte-by-byte comparison of the contents.

Code origin: Avalon

Parameters:
  `file1` - the first file
  `file2` - the second file
Returns:
  true if the content of the files are equal or they both don't exist, false otherwise
Throws:
  `IOException` - in case of an I/O error

#### contentEqualsIgnoreEOL

    public static boolean contentEqualsIgnoreEOL(File file1,
                                                 File file2,
                                                 String charsetName)
                                          throws IOException

Compares the contents of two files to determine if they are equal or not.

This method checks to see if the two files point to the same file, before resorting to line-by-line comparison of the contents.

Parameters:
  `file1` - the first file
  `file2` - the second file
  `charsetName` - the character encoding to be used. May be null, in which case the platform default is used
Returns:
  true if the content of the files are equal or neither exists, false otherwise
Throws:
  `IOException` - in case of an I/O error
Since:
  2.2
See Also:
  `IOUtils.contentEqualsIgnoreEOL(Reader, Reader)`

#### toFile

    public static File toFile(URL url)

Convert from a `URL` to a `File`.

From version 1.1 this method will decode the URL. Syntax such as `file:///my%20docs/file.txt` will be correctly decoded to `/my docs/file.txt`. Starting with version 1.5, this method uses UTF-8 to decode percent-encoded octets to characters. Additionally, malformed percent-encoded octets are handled leniently by passing them through literally.

Parameters:
  `url` - the file URL to convert, `null` returns `null`
Returns:
  the equivalent `File` object, or `null` if the URL's protocol is not `file`

#### toFiles

    public static File[] toFiles(URL[] urls)

Converts each of an array of `URL` to a `File`.

Returns an array of the same size as the input. If the input is `null`, an empty array is returned. If the input contains `null`, the output array contains `null` at the same index.

This method will decode the URL. Syntax such as `file:///my%20docs/file.txt` will be correctly decoded to `/my docs/file.txt`.

Parameters:
  `urls` - the file URLs to convert, `null` returns empty array
Returns:
  a non-`null` array of Files matching the input, with a `null` item if there was a `null` at that index in the input array
Throws:
  `IllegalArgumentException` - if any file is not a URL file
  `IllegalArgumentException` - if any file is incorrectly encoded
Since:
  1.1

#### toURLs

    public static URL[] toURLs(File[] files)
                        throws IOException

Converts each of an array of `File` to a `URL`.

Returns an array of the same size as the input.

Parameters:
  `files` - the files to convert, must not be `null`
Returns:
  an array of URLs matching the input
Throws:
  `IOException` - if a file cannot be converted
  `NullPointerException` - if the parameter is null

#### copyFileToDirectory

    public static void copyFileToDirectory(File srcFile,
                                           File destDir)
                                    throws IOException

Copies a file to a directory preserving the file date.

This method copies the contents of the specified source file to a file of the same name in the specified destination directory. The destination directory is created if it does not exist. If the destination file exists, then this method will overwrite it.

Note: This method tries to preserve the file's last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that the operation will succeed. If the modification operation fails, no indication is provided.

Parameters:
  `srcFile` - an existing file to copy, must not be `null`
  `destDir` - the directory to place the copy in, must not be `null`
Throws:
  `NullPointerException` - if source or destination is null
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
See Also:
  `copyFile(File, File, boolean)`

#### copyFileToDirectory

    public static void copyFileToDirectory(File srcFile,
                                           File destDir,
                                           boolean preserveFileDate)
                                    throws IOException

Copies a file to a directory optionally preserving the file date.

This method copies the contents of the specified source file to a file of the same name in the specified destination directory. The destination directory is created if it does not exist. If the destination file exists, then this method will overwrite it.

Note: Setting `preserveFileDate` to `true` tries to preserve the file's last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that the operation will succeed. If the modification operation fails, no indication is provided.

Parameters:
  `srcFile` - an existing file to copy, must not be `null`
  `destDir` - the directory to place the copy in, must not be `null`
  `preserveFileDate` - true if the file date of the copy should be the same as the original
Throws:
  `NullPointerException` - if source or destination is `null`
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
  `IOException` - if the output file length is not the same as the input file length after the copy completes
Since:
  1.3
See Also:
  `copyFile(File, File, boolean)`

#### copyFile

    public static void copyFile(File srcFile,
                                File destFile)
                         throws IOException

Copies a file to a new location preserving the file date.

This method copies the contents of the specified source file to the specified destination file. The directory holding the destination file is created if it does not exist. If the destination file exists, then this method will overwrite it.

Note: This method tries to preserve the file's last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that the operation will succeed. If the modification operation fails, no indication is provided.

Parameters:
  `srcFile` - an existing file to copy, must not be `null`
  `destFile` - the new file, must not be `null`
Throws:
  `NullPointerException` - if source or destination is `null`
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
  `IOException` - if the output file length is not the same as the input file length after the copy completes
See Also:
  `copyFileToDirectory(File, File)`, `copyFile(File, File, boolean)`

#### copyFile

    public static void copyFile(File srcFile,
                                File destFile,
                                boolean preserveFileDate)
                         throws IOException

Copies a file to a new location.

This method copies the contents of the specified source file to the specified destination file. The directory holding the destination file is created if it does not exist. If the destination file exists, then this method will overwrite it.

Note: Setting `preserveFileDate` to `true` tries to preserve the file's last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that the operation will succeed. If the modification operation fails, no indication is provided.

Parameters:
  `srcFile` - an existing file to copy, must not be `null`
  `destFile` - the new file, must not be `null`
  `preserveFileDate` - true if the file date of the copy should be the same as the original
Throws:
  `NullPointerException` - if source or destination is `null`
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
  `IOException` - if the output file length is not the same as the input file length after the copy completes
See Also:
  `copyFileToDirectory(File, File, boolean)`, `doCopyFile(File, File, boolean)`

#### copyFile

    public static long copyFile(File input,
                                OutputStream output)
                         throws IOException

Copy bytes from a `File` to an `OutputStream`.

This method buffers the input internally, so there is no need to use a `BufferedInputStream`.

Parameters:
  `input` - the `File` to read from
  `output` - the `OutputStream` to write to
Returns:
  the number of bytes copied
Throws:
  `NullPointerException` - if the input or output is null
  `IOException` - if an I/O error occurs
Since:
  2.1

#### copyDirectoryToDirectory

    public static void copyDirectoryToDirectory(File srcDir,
                                                File destDir)
                                         throws IOException

Copies a directory to within another directory preserving the file dates.

This method copies the source directory and all its contents to a directory of the same name in the specified destination directory.

The destination directory is created if it does not exist. If the destination directory did exist, then this method merges the source with the destination, with the source taking precedence.

Note: This method tries to preserve the files' last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that those operations will succeed. If the modification operation fails, no indication is provided.

Parameters:
  `srcDir` - an existing directory to copy, must not be `null`
  `destDir` - the directory to place the copy in, must not be `null`
Throws:
  `NullPointerException` - if source or destination is `null`
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
Since:
  1.2

#### copyDirectory

    public static void copyDirectory(File srcDir,
                                     File destDir)
                              throws IOException

Copies a whole directory to a new location preserving the file dates.

This method copies the specified directory and all its child directories and files to the specified destination. The destination is the new location and name of the directory.

The destination directory is created if it does not exist. If the destination directory did exist, then this method merges the source with the destination, with the source taking precedence.

Note: This method tries to preserve the files' last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that those operations will succeed. If the modification operation fails, no indication is provided.

Parameters:
  `srcDir` - an existing directory to copy, must not be `null`
  `destDir` - the new directory, must not be `null`
Throws:
  `NullPointerException` - if source or destination is `null`
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
Since:
  1.1

#### copyDirectory

    public static void copyDirectory(File srcDir,
                                     File destDir,
                                     boolean preserveFileDate)
                              throws IOException

Copies a whole directory to a new location.

This method copies the contents of the specified source directory to within the specified destination directory.

The destination directory is created if it does not exist. If the destination directory did exist, then this method merges the source with the destination, with the source taking precedence.

Note: Setting `preserveFileDate` to `true` tries to preserve the files' last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that those operations will succeed. If the modification operation fails, no indication is provided.

Parameters:
  `srcDir` - an existing directory to copy, must not be `null`
  `destDir` - the new directory, must not be `null`
  `preserveFileDate` - true if the file date of the copy should be the same as the original
Throws:
  `NullPointerException` - if source or destination is `null`
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
Since:
  1.1

#### copyDirectory

    public static void copyDirectory(File srcDir,
                                     File destDir,
                                     FileFilter filter)
                              throws IOException

Copies a filtered directory to a new location preserving the file dates.

This method copies the contents of the specified source directory to within the specified destination directory.

The destination directory is created if it does not exist. If the destination directory did exist, then this method merges the source with the destination, with the source taking precedence.

Note: This method tries to preserve the files' last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that those operations will succeed. If the modification operation fails, no indication is provided.

### Example: Copy directories only

      // only copy the directory structure
      FileUtils.copyDirectory(srcDir, destDir, DirectoryFileFilter.DIRECTORY);

### Example: Copy directories and txt files

      // Create a filter for ".txt" files
      IOFileFilter txtSuffixFilter = FileFilterUtils.suffixFileFilter(".txt");
      IOFileFilter txtFiles = FileFilterUtils.andFileFilter(FileFileFilter.FILE, txtSuffixFilter);

      // Create a filter for either directories or ".txt" files
      FileFilter filter = FileFilterUtils.orFileFilter(DirectoryFileFilter.DIRECTORY, txtFiles);

      // Copy using the filter
      FileUtils.copyDirectory(srcDir, destDir, filter);

Parameters:
  `srcDir` - an existing directory to copy, must not be `null`
  `destDir` - the new directory, must not be `null`
  `filter` - the filter to apply, null means copy all directories and files should be the same as the original
Throws:
  `NullPointerException` - if source or destination is `null`
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
Since:
  1.4

#### copyDirectory

    public static void copyDirectory(File srcDir,
                                     File destDir,
                                     FileFilter filter,
                                     boolean preserveFileDate)
                              throws IOException

Copies a filtered directory to a new location.

This method copies the contents of the specified source directory to within the specified destination directory.

The destination directory is created if it does not exist. If the destination directory did exist, then this method merges the source with the destination, with the source taking precedence.

Note: Setting `preserveFileDate` to `true` tries to preserve the files' last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that those operations will succeed. If the modification operation fails, no indication is provided.

### Example: Copy directories only

      // only copy the directory structure
      FileUtils.copyDirectory(srcDir, destDir, DirectoryFileFilter.DIRECTORY, false);

### Example: Copy directories and txt files

      // Create a filter for ".txt" files
      IOFileFilter txtSuffixFilter = FileFilterUtils.suffixFileFilter(".txt");
      IOFileFilter txtFiles = FileFilterUtils.andFileFilter(FileFileFilter.FILE, txtSuffixFilter);

      // Create a filter for either directories or ".txt" files
      FileFilter filter = FileFilterUtils.orFileFilter(DirectoryFileFilter.DIRECTORY, txtFiles);

      // Copy using the filter
      FileUtils.copyDirectory(srcDir, destDir, filter, false);

Parameters:
  `srcDir` - an existing directory to copy, must not be `null`
  `destDir` - the new directory, must not be `null`
  `filter` - the filter to apply, null means copy all directories and files
  `preserveFileDate` - true if the file date of the copy should be the same as the original
Throws:
  `NullPointerException` - if source or destination is `null`
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
Since:
  1.4

#### copyURLToFile

    public static void copyURLToFile(URL source,
                                     File destination)
                              throws IOException

Copies bytes from the URL `source` to a file `destination`. The directories up to `destination` will be created if they don't already exist. `destination` will be overwritten if it already exists.

Warning: this method does not set a connection or read timeout and thus might block forever. Use `copyURLToFile(URL, File, int, int)` with reasonable timeouts to prevent this.

Parameters:
  `source` - the `URL` to copy bytes from, must not be `null`
  `destination` - the non-directory `File` to write bytes to (possibly overwriting), must not be `null`
Throws:
  `IOException` - if `source` URL cannot be opened
  `IOException` - if `destination` is a directory
  `IOException` - if `destination` cannot be written
  `IOException` - if `destination` needs creating but can't be
  `IOException` - if an IO error occurs during copying

#### copyURLToFile

    public static void copyURLToFile(URL source,
                                     File destination,
                                     int connectionTimeout,
                                     int readTimeout)
                              throws IOException

Copies bytes from the URL `source` to a file `destination`. The directories up to `destination` will be created if they don't already exist. `destination` will be overwritten if it already exists.

Parameters:
  `source` - the `URL` to copy bytes from, must not be `null`
  `destination` - the non-directory `File` to write bytes to (possibly overwriting), must not be `null`
  `connectionTimeout` - the number of milliseconds until this method will timeout if no connection could be established to the `source`
  `readTimeout` - the number of milliseconds until this method will timeout if no data could be read from the `source`
Throws:
  `IOException` - if `source` URL cannot be opened
  `IOException` - if `destination` is a directory
  `IOException` - if `destination` cannot be written
  `IOException` - if `destination` needs creating but can't be
  `IOException` - if an IO error occurs during copying
Since:
  2.0

#### copyInputStreamToFile

    public static void copyInputStreamToFile(InputStream source,
                                             File destination)
                                      throws IOException

Copies bytes from an `InputStream` `source` to a file `destination`. The directories up to `destination` will be created if they don't already exist. `destination` will be overwritten if it already exists. The `source` stream is closed. See `copyToFile(InputStream, File)` for a method that does not close the input stream.

Parameters:
  `source` - the `InputStream` to copy bytes from, must not be `null`, will be closed
  `destination` - the non-directory `File` to write bytes to (possibly overwriting), must not be `null`
Throws:
  `IOException` - if `destination` is a directory
  `IOException` - if `destination` cannot be written
  `IOException` - if `destination` needs creating but can't be
  `IOException` - if an IO error occurs during copying
Since:
  2.0

#### copyToFile

    public static void copyToFile(InputStream source,
                                  File destination)
                           throws IOException

Copies bytes from an `InputStream` `source` to a file `destination`. The directories up to `destination` will be created if they don't already exist. `destination` will be overwritten if it already exists. The `source` stream is left open, e.g. for use with `ZipInputStream`. See `copyInputStreamToFile(InputStream, File)` for a method that closes the input stream.

Parameters:
  `source` - the `InputStream` to copy bytes from, must not be `null`
  `destination` - the non-directory `File` to write bytes to (possibly overwriting), must not be `null`
Throws:
  `IOException` - if `destination` is a directory
  `IOException` - if `destination` cannot be written
  `IOException` - if `destination` needs creating but can't be
  `IOException` - if an IO error occurs during copying
Since:
  2.5

#### copyToDirectory

    public static void copyToDirectory(File src,
                                       File destDir)
                                throws IOException

Copies a file or directory to within another directory preserving the file dates.

This method copies the source file or directory, along all its contents, to a directory of the same name in the specified destination directory.

The destination directory is created if it does not exist. If the destination directory did exist, then this method merges the source with the destination, with the source taking precedence.

Note: This method tries to preserve the files' last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that those operations will succeed. If the modification operation fails, no indication is provided.

Parameters:
  `src` - an existing file or directory to copy, must not be `null`
  `destDir` - the directory to place the copy in, must not be `null`
Throws:
  `NullPointerException` - if source or destination is `null`
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
Since:
  2.6
See Also:
  `copyDirectoryToDirectory(File, File)`, `copyFileToDirectory(File, File)`

#### copyToDirectory

    public static void copyToDirectory(Iterable<File> srcs,
                                       File destDir)
                                throws IOException

Copies a files to a directory preserving each file's date.

This method copies the contents of the specified source files to a file of the same name in the specified destination directory. The destination directory is created if it does not exist. If the destination file exists, then this method will overwrite it.

Note: This method tries to preserve the file's last modified date/times using `File.setLastModified(long)`, however it is not guaranteed that the operation will succeed. If the modification operation fails, no indication is provided.

Parameters:
  `srcs` - a existing files to copy, must not be `null`
  `destDir` - the directory to place the copy in, must not be `null`
Throws:
  `NullPointerException` - if source or destination is null
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs during copying
Since:
  2.6
See Also:
  `copyFileToDirectory(File, File)`

#### deleteDirectory

    public static void deleteDirectory(File directory)
                                throws IOException

Deletes a directory recursively.

Parameters:
  `directory` - directory to delete
Throws:
  `IOException` - in case deletion is unsuccessful
  `IllegalArgumentException` - if `directory` does not exist or is not a directory

#### deleteQuietly

    public static boolean deleteQuietly(File file)

Deletes a file, never throwing an exception. If file is a directory, delete it and all sub-directories.

The difference between File.delete() and this method are:

- A directory to be deleted does not have to be empty.
- No exceptions are thrown when a file or directory cannot be deleted.

Parameters:
  `file` - file or directory to delete, can be `null`
Returns:
  `true` if the file or directory was deleted, otherwise `false`
Since:
  1.4

#### directoryContains

    public static boolean directoryContains(File directory,
                                            File child)
                                     throws IOException

Determines whether the `parent` directory contains the `child` element (a file or directory).

Files are normalized before comparison.

Edge cases:

- A `directory` must not be null: if null, throw IllegalArgumentException
- A `directory` must be a directory: if not a directory, throw IllegalArgumentException
- A directory does not contain itself: return false
- A null child file is not contained in any parent: return false

Parameters:
  `directory` - the file to consider as the parent.
  `child` - the file to consider as the child.
Returns:
  true is the candidate leaf is under by the specified composite. False otherwise.
Throws:
  `IOException` - if an IO error occurs while checking the files.
  `IllegalArgumentException` - if `directory` is null or not a directory.
Since:
  2.2
See Also:
  `FilenameUtils.directoryContains(String, String)`

#### cleanDirectory

    public static void cleanDirectory(File directory)
                               throws IOException

Cleans a directory without deleting it.

Parameters:
  `directory` - directory to clean
Throws:
  `IOException` - in case cleaning is unsuccessful
  `IllegalArgumentException` - if `directory` does not exist or is not a directory

#### waitFor

    public static boolean waitFor(File file,
                                  int seconds)

Waits for NFS to propagate a file creation, imposing a timeout.

This method repeatedly tests `File.exists()` until it returns true up to the maximum time specified in seconds.

Parameters:
  `file` - the file to check, must not be `null`
  `seconds` - the maximum time in seconds to wait
Returns:
  true if file exists
Throws:
  `NullPointerException` - if the file is `null`

#### readFileToString

    public static String readFileToString(File file,
                                          Charset encoding)
                                   throws IOException

Reads the contents of a file into a String. The file is always closed.

Parameters:
  `file` - the file to read, must not be `null`
  `encoding` - the encoding to use, `null` means platform default
Returns:
  the file contents, never `null`
Throws:
  `IOException` - in case of an I/O error
Since:
  2.3

#### readFileToString

    public static String readFileToString(File file,
                                          String encoding)
                                   throws IOException

Reads the contents of a file into a String. The file is always closed.

Parameters:
  `file` - the file to read, must not be `null`
  `encoding` - the encoding to use, `null` means platform default
Returns:
  the file contents, never `null`
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedCharsetException` - thrown instead of `.UnsupportedEncodingException` in version 2.2 if the encoding is not supported.
Since:
  2.3

#### readFileToString

    @Deprecated
    public static String readFileToString(File file)
                                               throws IOException

Deprecated. 2.5 use `readFileToString(File, Charset)` instead (and specify the appropriate encoding)
Reads the contents of a file into a String using the default encoding for the VM. The file is always closed.

Parameters:
  `file` - the file to read, must not be `null`
Returns:
  the file contents, never `null`
Throws:
  `IOException` - in case of an I/O error
Since:
  1.3.1

#### readFileToByteArray

    public static byte[] readFileToByteArray(File file)
                                      throws IOException

Reads the contents of a file into a byte array. The file is always closed.

Parameters:
  `file` - the file to read, must not be `null`
Returns:
  the file contents, never `null`
Throws:
  `IOException` - in case of an I/O error
Since:
  1.1

#### readLines

    public static List<String> readLines(File file,
                                         Charset encoding)
                                  throws IOException

Reads the contents of a file line by line to a List of Strings. The file is always closed.

Parameters:
  `file` - the file to read, must not be `null`
  `encoding` - the encoding to use, `null` means platform default
Returns:
  the list of Strings representing each line in the file, never `null`
Throws:
  `IOException` - in case of an I/O error
Since:
  2.3

#### readLines

    public static List<String> readLines(File file,
                                         String encoding)
                                  throws IOException

Reads the contents of a file line by line to a List of Strings. The file is always closed.

Parameters:
  `file` - the file to read, must not be `null`
  `encoding` - the encoding to use, `null` means platform default
Returns:
  the list of Strings representing each line in the file, never `null`
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedCharsetException` - thrown instead of `.UnsupportedEncodingException` in version 2.2 if the encoding is not supported.
Since:
  1.1

#### readLines

    @Deprecated
    public static List<String> readLines(File file)
                                              throws IOException

Deprecated. 2.5 use `readLines(File, Charset)` instead (and specify the appropriate encoding)
Reads the contents of a file line by line to a List of Strings using the default encoding for the VM. The file is always closed.

Parameters:
  `file` - the file to read, must not be `null`
Returns:
  the list of Strings representing each line in the file, never `null`
Throws:
  `IOException` - in case of an I/O error
Since:
  1.3

#### lineIterator

    public static LineIterator lineIterator(File file,
                                            String encoding)
                                     throws IOException

Returns an Iterator for the lines in a `File`.

This method opens an `InputStream` for the file. When you have finished with the iterator you should close the stream to free internal resources. This can be done by calling the `LineIterator.close()` or `LineIterator.closeQuietly(LineIterator)` method.

The recommended usage pattern is:

     LineIterator it = FileUtils.lineIterator(file, "UTF-8");
     try {
       while (it.hasNext()) {
         String line = it.nextLine();
         /// do something with line
       }
     } finally {
       LineIterator.closeQuietly(iterator);
     }

If an exception occurs during the creation of the iterator, the underlying stream is closed.

Parameters:
  `file` - the file to open for input, must not be `null`
  `encoding` - the encoding to use, `null` means platform default
Returns:
  an Iterator of the lines in the file, never `null`
Throws:
  `IOException` - in case of an I/O error (file closed)
Since:
  1.2

#### lineIterator

    public static LineIterator lineIterator(File file)
                                     throws IOException

Returns an Iterator for the lines in a `File` using the default encoding for the VM.

Parameters:
  `file` - the file to open for input, must not be `null`
Returns:
  an Iterator of the lines in the file, never `null`
Throws:
  `IOException` - in case of an I/O error (file closed)
Since:
  1.3
See Also:
  `lineIterator(File, String)`

#### writeStringToFile

    public static void writeStringToFile(File file,
                                         String data,
                                         Charset encoding)
                                  throws IOException

Writes a String to a file creating the file if it does not exist.

NOTE: As from v1.3, the parent directories of the file will be created if they do not exist.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
  `encoding` - the encoding to use, `null` means platform default
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedEncodingException` - if the encoding is not supported by the VM
Since:
  2.4

#### writeStringToFile

    public static void writeStringToFile(File file,
                                         String data,
                                         String encoding)
                                  throws IOException

Writes a String to a file creating the file if it does not exist.

NOTE: As from v1.3, the parent directories of the file will be created if they do not exist.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
  `encoding` - the encoding to use, `null` means platform default
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedEncodingException` - if the encoding is not supported by the VM

#### writeStringToFile

    public static void writeStringToFile(File file,
                                         String data,
                                         Charset encoding,
                                         boolean append)
                                  throws IOException

Writes a String to a file creating the file if it does not exist.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
  `encoding` - the encoding to use, `null` means platform default
  `append` - if `true`, then the String will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
Since:
  2.3

#### writeStringToFile

    public static void writeStringToFile(File file,
                                         String data,
                                         String encoding,
                                         boolean append)
                                  throws IOException

Writes a String to a file creating the file if it does not exist.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
  `encoding` - the encoding to use, `null` means platform default
  `append` - if `true`, then the String will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedCharsetException` - thrown instead of `.UnsupportedEncodingException` in version 2.2 if the encoding is not supported by the VM
Since:
  2.1

#### writeStringToFile

    @Deprecated
    public static void writeStringToFile(File file,
                                                     String data)
                                              throws IOException

Deprecated. 2.5 use `writeStringToFile(File, String, Charset)` instead (and specify the appropriate encoding)
Writes a String to a file creating the file if it does not exist using the default encoding for the VM.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
Throws:
  `IOException` - in case of an I/O error

#### writeStringToFile

    @Deprecated
    public static void writeStringToFile(File file,
                                                     String data,
                                                     boolean append)
                                              throws IOException

Deprecated. 2.5 use `writeStringToFile(File, String, Charset, boolean)` instead (and specify the appropriate encoding)
Writes a String to a file creating the file if it does not exist using the default encoding for the VM.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
  `append` - if `true`, then the String will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
Since:
  2.1

#### write

    @Deprecated
    public static void write(File file,
                                         CharSequence data)
                                  throws IOException

Deprecated. 2.5 use `write(File, CharSequence, Charset)` instead (and specify the appropriate encoding)
Writes a CharSequence to a file creating the file if it does not exist using the default encoding for the VM.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
Throws:
  `IOException` - in case of an I/O error
Since:
  2.0

#### write

    @Deprecated
    public static void write(File file,
                                         CharSequence data,
                                         boolean append)
                                  throws IOException

Deprecated. 2.5 use `write(File, CharSequence, Charset, boolean)` instead (and specify the appropriate encoding)
Writes a CharSequence to a file creating the file if it does not exist using the default encoding for the VM.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
  `append` - if `true`, then the data will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
Since:
  2.1

#### write

    public static void write(File file,
                             CharSequence data,
                             Charset encoding)
                      throws IOException

Writes a CharSequence to a file creating the file if it does not exist.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
  `encoding` - the encoding to use, `null` means platform default
Throws:
  `IOException` - in case of an I/O error
Since:
  2.3

#### write

    public static void write(File file,
                             CharSequence data,
                             String encoding)
                      throws IOException

Writes a CharSequence to a file creating the file if it does not exist.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
  `encoding` - the encoding to use, `null` means platform default
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedEncodingException` - if the encoding is not supported by the VM
Since:
  2.0

#### write

    public static void write(File file,
                             CharSequence data,
                             Charset encoding,
                             boolean append)
                      throws IOException

Writes a CharSequence to a file creating the file if it does not exist.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
  `encoding` - the encoding to use, `null` means platform default
  `append` - if `true`, then the data will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
Since:
  2.3

#### write

    public static void write(File file,
                             CharSequence data,
                             String encoding,
                             boolean append)
                      throws IOException

Writes a CharSequence to a file creating the file if it does not exist.

Parameters:
  `file` - the file to write
  `data` - the content to write to the file
  `encoding` - the encoding to use, `null` means platform default
  `append` - if `true`, then the data will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedCharsetException` - thrown instead of `.UnsupportedEncodingException` in version 2.2 if the encoding is not supported by the VM
Since:
  2.1

#### writeByteArrayToFile

    public static void writeByteArrayToFile(File file,
                                            byte[] data)
                                     throws IOException

Writes a byte array to a file creating the file if it does not exist.

NOTE: As from v1.3, the parent directories of the file will be created if they do not exist.

Parameters:
  `file` - the file to write to
  `data` - the content to write to the file
Throws:
  `IOException` - in case of an I/O error
Since:
  1.1

#### writeByteArrayToFile

    public static void writeByteArrayToFile(File file,
                                            byte[] data,
                                            boolean append)
                                     throws IOException

Writes a byte array to a file creating the file if it does not exist.

Parameters:
  `file` - the file to write to
  `data` - the content to write to the file
  `append` - if `true`, then bytes will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
Since:
  2.1

#### writeByteArrayToFile

    public static void writeByteArrayToFile(File file,
                                            byte[] data,
                                            int off,
                                            int len)
                                     throws IOException

Writes `len` bytes from the specified byte array starting at offset `off` to a file, creating the file if it does not exist.

Parameters:
  `file` - the file to write to
  `data` - the content to write to the file
  `off` - the start offset in the data
  `len` - the number of bytes to write
Throws:
  `IOException` - in case of an I/O error
Since:
  2.5

#### writeByteArrayToFile

    public static void writeByteArrayToFile(File file,
                                            byte[] data,
                                            int off,
                                            int len,
                                            boolean append)
                                     throws IOException

Writes `len` bytes from the specified byte array starting at offset `off` to a file, creating the file if it does not exist.

Parameters:
  `file` - the file to write to
  `data` - the content to write to the file
  `off` - the start offset in the data
  `len` - the number of bytes to write
  `append` - if `true`, then bytes will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
Since:
  2.5

#### writeLines

    public static void writeLines(File file,
                                  String encoding,
                                  Collection<?> lines)
                           throws IOException

Writes the `toString()` value of each item in a collection to the specified `File` line by line. The specified character encoding and the default line ending will be used.

NOTE: As from v1.3, the parent directories of the file will be created if they do not exist.

Parameters:
  `file` - the file to write to
  `encoding` - the encoding to use, `null` means platform default
  `lines` - the lines to write, `null` entries produce blank lines
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedEncodingException` - if the encoding is not supported by the VM
Since:
  1.1

#### writeLines

    public static void writeLines(File file,
                                  String encoding,
                                  Collection<?> lines,
                                  boolean append)
                           throws IOException

Writes the `toString()` value of each item in a collection to the specified `File` line by line, optionally appending. The specified character encoding and the default line ending will be used.

Parameters:
  `file` - the file to write to
  `encoding` - the encoding to use, `null` means platform default
  `lines` - the lines to write, `null` entries produce blank lines
  `append` - if `true`, then the lines will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedEncodingException` - if the encoding is not supported by the VM
Since:
  2.1

#### writeLines

    public static void writeLines(File file,
                                  Collection<?> lines)
                           throws IOException

Writes the `toString()` value of each item in a collection to the specified `File` line by line. The default VM encoding and the default line ending will be used.

Parameters:
  `file` - the file to write to
  `lines` - the lines to write, `null` entries produce blank lines
Throws:
  `IOException` - in case of an I/O error
Since:
  1.3

#### writeLines

    public static void writeLines(File file,
                                  Collection<?> lines,
                                  boolean append)
                           throws IOException

Writes the `toString()` value of each item in a collection to the specified `File` line by line. The default VM encoding and the default line ending will be used.

Parameters:
  `file` - the file to write to
  `lines` - the lines to write, `null` entries produce blank lines
  `append` - if `true`, then the lines will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
Since:
  2.1

#### writeLines

    public static void writeLines(File file,
                                  String encoding,
                                  Collection<?> lines,
                                  String lineEnding)
                           throws IOException

Writes the `toString()` value of each item in a collection to the specified `File` line by line. The specified character encoding and the line ending will be used.

NOTE: As from v1.3, the parent directories of the file will be created if they do not exist.

Parameters:
  `file` - the file to write to
  `encoding` - the encoding to use, `null` means platform default
  `lines` - the lines to write, `null` entries produce blank lines
  `lineEnding` - the line separator to use, `null` is system default
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedEncodingException` - if the encoding is not supported by the VM
Since:
  1.1

#### writeLines

    public static void writeLines(File file,
                                  String encoding,
                                  Collection<?> lines,
                                  String lineEnding,
                                  boolean append)
                           throws IOException

Writes the `toString()` value of each item in a collection to the specified `File` line by line. The specified character encoding and the line ending will be used.

Parameters:
  `file` - the file to write to
  `encoding` - the encoding to use, `null` means platform default
  `lines` - the lines to write, `null` entries produce blank lines
  `lineEnding` - the line separator to use, `null` is system default
  `append` - if `true`, then the lines will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
  `UnsupportedEncodingException` - if the encoding is not supported by the VM
Since:
  2.1

#### writeLines

    public static void writeLines(File file,
                                  Collection<?> lines,
                                  String lineEnding)
                           throws IOException

Writes the `toString()` value of each item in a collection to the specified `File` line by line. The default VM encoding and the specified line ending will be used.

Parameters:
  `file` - the file to write to
  `lines` - the lines to write, `null` entries produce blank lines
  `lineEnding` - the line separator to use, `null` is system default
Throws:
  `IOException` - in case of an I/O error
Since:
  1.3

#### writeLines

    public static void writeLines(File file,
                                  Collection<?> lines,
                                  String lineEnding,
                                  boolean append)
                           throws IOException

Writes the `toString()` value of each item in a collection to the specified `File` line by line. The default VM encoding and the specified line ending will be used.

Parameters:
  `file` - the file to write to
  `lines` - the lines to write, `null` entries produce blank lines
  `lineEnding` - the line separator to use, `null` is system default
  `append` - if `true`, then the lines will be added to the end of the file rather than overwriting
Throws:
  `IOException` - in case of an I/O error
Since:
  2.1

#### forceDelete

    public static void forceDelete(File file)
                            throws IOException

Deletes a file. If file is a directory, delete it and all sub-directories.

The difference between File.delete() and this method are:

- A directory to be deleted does not have to be empty.
- You get exceptions when a file or directory cannot be deleted. (java.io.File methods returns a boolean)

Parameters:
  `file` - file or directory to delete, must not be `null`
Throws:
  `NullPointerException` - if the directory is `null`
  `FileNotFoundException` - if the file was not found
  `IOException` - in case deletion is unsuccessful

#### forceDeleteOnExit

    public static void forceDeleteOnExit(File file)
                                  throws IOException

Schedules a file to be deleted when JVM exits. If file is directory delete it and all sub-directories.

Parameters:
  `file` - file or directory to delete, must not be `null`
Throws:
  `NullPointerException` - if the file is `null`
  `IOException` - in case deletion is unsuccessful

#### forceMkdir

    public static void forceMkdir(File directory)
                           throws IOException

Makes a directory, including any necessary but nonexistent parent directories. If a file already exists with specified name but it is not a directory then an IOException is thrown. If the directory cannot be created (or does not already exist) then an IOException is thrown.

Parameters:
  `directory` - directory to create, must not be `null`
Throws:
  `NullPointerException` - if the directory is `null`
  `IOException` - if the directory cannot be created or the file already exists but is not a directory

#### forceMkdirParent

    public static void forceMkdirParent(File file)
                                 throws IOException

Makes any necessary but nonexistent parent directories for a given File. If the parent directory cannot be created then an IOException is thrown.

Parameters:
  `file` - file with parent to create, must not be `null`
Throws:
  `NullPointerException` - if the file is `null`
  `IOException` - if the parent directory cannot be created
Since:
  2.5

#### sizeOf

    public static long sizeOf(File file)

Returns the size of the specified file or directory. If the provided `File` is a regular file, then the file's length is returned. If the argument is a directory, then the size of the directory is calculated recursively. If a directory or subdirectory is security restricted, its size will not be included.

Note that overflow is not detected, and the return value may be negative if overflow occurs. See `sizeOfAsBigInteger(File)` for an alternative method that does not overflow.

Parameters:
  `file` - the regular file or directory to return the size of (must not be `null`).
Returns:
  the length of the file, or recursive size of the directory, provided (in bytes).
Throws:
  `NullPointerException` - if the file is `null`
  `IllegalArgumentException` - if the file does not exist.
Since:
  2.0

#### sizeOfAsBigInteger

    public static BigInteger sizeOfAsBigInteger(File file)

Returns the size of the specified file or directory. If the provided `File` is a regular file, then the file's length is returned. If the argument is a directory, then the size of the directory is calculated recursively. If a directory or subdirectory is security restricted, its size will not be included.

Parameters:
  `file` - the regular file or directory to return the size of (must not be `null`).
Returns:
  the length of the file, or recursive size of the directory, provided (in bytes).
Throws:
  `NullPointerException` - if the file is `null`
  `IllegalArgumentException` - if the file does not exist.
Since:
  2.4

#### sizeOfDirectory

    public static long sizeOfDirectory(File directory)

Counts the size of a directory recursively (sum of the length of all files).

Note that overflow is not detected, and the return value may be negative if overflow occurs. See `sizeOfDirectoryAsBigInteger(File)` for an alternative method that does not overflow.

Parameters:
  `directory` - directory to inspect, must not be `null`
Returns:
  size of directory in bytes, 0 if directory is security restricted, a negative number when the real total is greater than `Long.MAX_VALUE`.
Throws:
  `NullPointerException` - if the directory is `null`

#### sizeOfDirectoryAsBigInteger

    public static BigInteger sizeOfDirectoryAsBigInteger(File directory)

Counts the size of a directory recursively (sum of the length of all files).

Parameters:
  `directory` - directory to inspect, must not be `null`
Returns:
  size of directory in bytes, 0 if directory is security restricted.
Throws:
  `NullPointerException` - if the directory is `null`
Since:
  2.4

#### isFileNewer

    public static boolean isFileNewer(File file,
                                      File reference)

Tests if the specified `File` is newer than the reference `File`.

Parameters:
  `file` - the `File` of which the modification date must be compared, must not be `null`
  `reference` - the `File` of which the modification date is used, must not be `null`
Returns:
  true if the `File` exists and has been modified more recently than the reference `File`
Throws:
  `IllegalArgumentException` - if the file is `null`
  `IllegalArgumentException` - if the reference file is `null` or doesn't exist

#### isFileNewer

    public static boolean isFileNewer(File file,
                                      Date date)

Tests if the specified `File` is newer than the specified `Date`.

Parameters:
  `file` - the `File` of which the modification date must be compared, must not be `null`
  `date` - the date reference, must not be `null`
Returns:
  true if the `File` exists and has been modified after the given `Date`.
Throws:
  `IllegalArgumentException` - if the file is `null`
  `IllegalArgumentException` - if the date is `null`

#### isFileNewer

    public static boolean isFileNewer(File file,
                                      long timeMillis)

Tests if the specified `File` is newer than the specified time reference.

Parameters:
  `file` - the `File` of which the modification date must be compared, must not be `null`
  `timeMillis` - the time reference measured in milliseconds since the epoch (00:00:00 GMT, January 1, 1970)
Returns:
  true if the `File` exists and has been modified after the given time reference.
Throws:
  `IllegalArgumentException` - if the file is `null`

#### isFileOlder

    public static boolean isFileOlder(File file,
                                      File reference)

Tests if the specified `File` is older than the reference `File`.

Parameters:
  `file` - the `File` of which the modification date must be compared, must not be `null`
  `reference` - the `File` of which the modification date is used, must not be `null`
Returns:
  true if the `File` exists and has been modified before the reference `File`
Throws:
  `IllegalArgumentException` - if the file is `null`
  `IllegalArgumentException` - if the reference file is `null` or doesn't exist

#### isFileOlder

    public static boolean isFileOlder(File file,
                                      Date date)

Tests if the specified `File` is older than the specified `Date`.

Parameters:
  `file` - the `File` of which the modification date must be compared, must not be `null`
  `date` - the date reference, must not be `null`
Returns:
  true if the `File` exists and has been modified before the given `Date`.
Throws:
  `IllegalArgumentException` - if the file is `null`
  `IllegalArgumentException` - if the date is `null`

#### isFileOlder

    public static boolean isFileOlder(File file,
                                      long timeMillis)

Tests if the specified `File` is older than the specified time reference.

Parameters:
  `file` - the `File` of which the modification date must be compared, must not be `null`
  `timeMillis` - the time reference measured in milliseconds since the epoch (00:00:00 GMT, January 1, 1970)
Returns:
  true if the `File` exists and has been modified before the given time reference.
Throws:
  `IllegalArgumentException` - if the file is `null`

#### checksumCRC32

    public static long checksumCRC32(File file)
                              throws IOException

Computes the checksum of a file using the CRC32 checksum routine. The value of the checksum is returned.

Parameters:
  `file` - the file to checksum, must not be `null`
Returns:
  the checksum value
Throws:
  `NullPointerException` - if the file or checksum is `null`
  `IllegalArgumentException` - if the file is a directory
  `IOException` - if an IO error occurs reading the file
Since:
  1.3

#### checksum

    public static Checksum checksum(File file,
                                    Checksum checksum)
                             throws IOException

Computes the checksum of a file using the specified checksum object. Multiple files may be checked using one `Checksum` instance if desired simply by reusing the same checksum object. For example:

       long csum = FileUtils.checksum(file, new CRC32()).getValue();

Parameters:
  `file` - the file to checksum, must not be `null`
  `checksum` - the checksum object to be used, must not be `null`
Returns:
  the checksum specified, updated with the content of the file
Throws:
  `NullPointerException` - if the file or checksum is `null`
  `IllegalArgumentException` - if the file is a directory
  `IOException` - if an IO error occurs reading the file
Since:
  1.3

#### moveDirectory

    public static void moveDirectory(File srcDir,
                                     File destDir)
                              throws IOException

Moves a directory.

When the destination directory is on another file system, do a "copy and delete".

Parameters:
  `srcDir` - the directory to be moved
  `destDir` - the destination directory
Throws:
  `NullPointerException` - if source or destination is `null`
  `FileExistsException` - if the destination directory exists
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs moving the file
Since:
  1.4

#### moveDirectoryToDirectory

    public static void moveDirectoryToDirectory(File src,
                                                File destDir,
                                                boolean createDestDir)
                                         throws IOException

Moves a directory to another directory.

Parameters:
  `src` - the file to be moved
  `destDir` - the destination file
  `createDestDir` - If `true` create the destination directory, otherwise if `false` throw an IOException
Throws:
  `NullPointerException` - if source or destination is `null`
  `FileExistsException` - if the directory exists in the destination directory
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs moving the file
Since:
  1.4

#### moveFile

    public static void moveFile(File srcFile,
                                File destFile)
                         throws IOException

Moves a file.

When the destination file is on another file system, do a "copy and delete".

Parameters:
  `srcFile` - the file to be moved
  `destFile` - the destination file
Throws:
  `NullPointerException` - if source or destination is `null`
  `FileExistsException` - if the destination file exists
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs moving the file
Since:
  1.4

#### moveFileToDirectory

    public static void moveFileToDirectory(File srcFile,
                                           File destDir,
                                           boolean createDestDir)
                                    throws IOException

Moves a file to a directory.

Parameters:
  `srcFile` - the file to be moved
  `destDir` - the destination file
  `createDestDir` - If `true` create the destination directory, otherwise if `false` throw an IOException
Throws:
  `NullPointerException` - if source or destination is `null`
  `FileExistsException` - if the destination file exists
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs moving the file
Since:
  1.4

#### moveToDirectory

    public static void moveToDirectory(File src,
                                       File destDir,
                                       boolean createDestDir)
                                throws IOException

Moves a file or directory to the destination directory.

When the destination is on another file system, do a "copy and delete".

Parameters:
  `src` - the file or directory to be moved
  `destDir` - the destination directory
  `createDestDir` - If `true` create the destination directory, otherwise if `false` throw an IOException
Throws:
  `NullPointerException` - if source or destination is `null`
  `FileExistsException` - if the directory or file exists in the destination directory
  `IOException` - if source or destination is invalid
  `IOException` - if an IO error occurs moving the file
Since:
  1.4

#### isSymlink

    public static boolean isSymlink(File file)
                             throws IOException

Determines whether the specified file is a Symbolic Link rather than an actual file.

Will not return true if there is a Symbolic Link anywhere in the path, only if the specific file is.

When using jdk1.7, this method delegates to `boolean java.nio.file.Files.isSymbolicLink(Path path)` Note: the current implementation always returns `false` if running on jkd1.6 and the system is detected as Windows using `FilenameUtils.isSystemWindows()`

For code that runs on Java 1.7 or later, use the following method instead:
`boolean java.nio.file.Files.isSymbolicLink(Path path)`

Parameters:
  `file` - the file to check
Returns:
  true if the file is a Symbolic Link
Throws:
  `IOException` - if an IO error occurs while checking the file
Since:
  2.0