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

Origin of code: Excalibur, Alexandria, Commons-Utils

Version:

$Id: FileUtils.java 384037 2006-03-07 22:26:37Z scolebourne $

Field Summary

static File[]	EMPTY_FILE_ARRAY An empty array of type File.
static long	ONE_GB The number of bytes in a gigabyte.
static long	ONE_KB The number of bytes in a kilobyte.
static long	ONE_MB The number of bytes in a megabyte.

Constructor Summary

FileUtils()
Instances should NOT be constructed in standard programming.

Method Summary

static String	byteCountToDisplaySize(long size) Returns a human-readable version of the file size, where the input represents a specific number of bytes.
static void	cleanDirectory(File directory) Clean a directory without deleting it.
static boolean	contentEquals(File file1, File file2) Compare the contents of two files to determine if they are equal or not.
static File[]	convertFileCollectionToFileArray(Collection 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	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 void	copyFileToDirectory(File srcFile, File destDir) Copies a file to a directory preserving the file date.
static void	copyURLToFile(URL source, File destination) Copies bytes from the URL source to a file destination.
static void	deleteDirectory(File directory) Recursively delete a directory.
static void	forceDelete(File file) Delete a file.
static void	forceDeleteOnExit(File file) Schedule a file to be deleted when JVM exits.
static void	forceMkdir(File directory) Make a directory, including any necessary but nonexistent parent directories.
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 Iterator	iterateFiles(File directory, IOFileFilter fileFilter, IOFileFilter dirFilter) Allows iteration over the files in given directory (and optionally its subdirectories).
static Iterator	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 LineIterator	lineIterator(File file, String encoding) Return an Iterator for the lines in a File.
static Collection	listFiles(File directory, IOFileFilter fileFilter, IOFileFilter dirFilter) Finds files within a given directory (and optionally its subdirectories).
static Collection	listFiles(File directory, String[] extensions, boolean recursive) Finds files within a given directory (and optionally its subdirectories) which match an array of extensions.
static byte[]	readFileToByteArray(File file) Reads the contents of a file into a byte array.
static String	readFileToString(File file, String encoding) Reads the contents of a file into a String.
static List	readLines(File file, String encoding) Reads the contents of a file line by line to a List of Strings.
static long	sizeOfDirectory(File directory) Recursively count size of a directory (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	writeByteArrayToFile(File file, byte[] data) Writes a byte array to a file creating the file if it does not exist.
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, String lineEnding) Writes the toString() value of each item in a collection to the specified File line by line.
static void	writeStringToFile(File file, String data, String encoding) 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_MB

public static final long ONE_MB

The number of bytes in a megabyte.

See Also:

Constant Field Values

ONE_GB

public static final long ONE_GB

The number of bytes in a gigabyte.

See Also:

Constant Field Values

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

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.

Parameters:

size - the number of bytes

Returns:

a human-readable display value (includes units)

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.

Parameters:

file - the File to touch

Throws:

IOException - If an I/O problem occurs

convertFileCollectionToFileArray

public static File[] convertFileCollectionToFileArray(Collection 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 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.

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 collection of java.io.File with the matching files

See Also:

FileFilterUtils, NameFileFilter

iterateFiles

public static Iterator 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).

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:

Commons IO 1.2

See Also:

FileFilterUtils, NameFileFilter

listFiles

public static Collection 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:

an collection of java.io.File with the matching files

iterateFiles

public static Iterator 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).

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:

Commons IO 1.2

contentEquals

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

Compare 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

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.

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

Throws:

IllegalArgumentException - if the file is incorrectly encoded

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:

Commons IO 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

Returns:

an array of URLs matching the input

Throws:

IOException - if a file cannot be converted

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.

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)

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.

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

See Also:

copyFileToDirectory(java.io.File, java.io.File)

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.

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

See Also:

copyFileToDirectory(java.io.File, java.io.File)

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.

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:

Commons IO 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.

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:

Commons IO 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.

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:

Commons IO 1.1

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.

Parameters:

source - A URL to copy bytes from.

destination - A non-directory File to write bytes to (possibly overwriting).

Throws:

IOException - if

• source URL cannot be opened
• destination cannot be written to
• an IO error occurs during copying

deleteDirectory

public static void deleteDirectory(File directory)
                            throws IOException

Recursively delete a directory.

Parameters:

directory - directory to delete

Throws:

IOException - in case deletion is unsuccessful

cleanDirectory

public static void cleanDirectory(File directory)
                           throws IOException

Clean a directory without deleting it.

Parameters:

directory - directory to clean

Throws:

IOException - in case cleaning is unsuccessful

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, not 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,
                                      String encoding)
                               throws IOException

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

There is no readFileToString method without encoding parameter because the default encoding can differ between platforms and will have inconsistent results.

Parameters:

file - the file to read

encoding - the encoding to use, null means platform default

Returns:

the file contents or null if read failed

Throws:

IOException - in case of an I/O error

UnsupportedEncodingException - if the encoding is not supported by the VM

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

Returns:

the file contents or null if read failed

Throws:

IOException - in case of an I/O error

Since:

Commons IO 1.1

readLines

public static List 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.

There is no readLines method without encoding parameter because the default encoding can differ between platforms and will have inconsistent results.

Parameters:

file - the file to read

encoding - the encoding to use, null means platform default

Returns:

the list of Strings representing each line in the file

Throws:

IOException - in case of an I/O error

UnsupportedEncodingException - if the encoding is not supported by the VM

Since:

Commons IO 1.1

lineIterator

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

Return 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.

There is no lineIterator method without encoding parameter because the default encoding can differ between platforms and will have inconsistent results.

Parameters:

file - the file to read

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:

Commons IO 1.2

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.

There is no writeStringToFile method without encoding parameter because the default encoding can differ between platforms and will have inconsistent results.

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

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.

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:

Commons IO 1.1

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.

There is no writeLines method without encoding parameter because the default encoding can differ between platforms and will have inconsistent results.

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:

Commons IO 1.1

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.

There is no writeLines method without encoding parameter because the default encoding can differ between platforms and will have inconsistent results.

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:

Commons IO 1.1

forceDelete

public static void forceDelete(File file)
                        throws IOException

Delete 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, not null

Throws:

NullPointerException - if the directory is null

IOException - in case deletion is unsuccessful

forceDeleteOnExit

public static void forceDeleteOnExit(File file)
                              throws IOException

Schedule 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, not null

Throws:

NullPointerException - if the file is null

IOException - in case deletion is unsuccessful

forceMkdir

public static void forceMkdir(File directory)
                       throws IOException

Make a directory, including any necessary but nonexistent parent directories. If there already exists a file with specified name or the directory cannot be created then an exception is thrown.

Parameters:

directory - directory to create, not null

Throws:

NullPointerException - if the directory is null

IOException - if the directory cannot be created

sizeOfDirectory

public static long sizeOfDirectory(File directory)

Recursively count size of a directory (sum of the length of all files).

Parameters:

directory - directory to inspect, not null

Returns:

size of directory in bytes, 0 if directory is security restricted

Throws:

NullPointerException - if the directory is null

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, not null

reference - the File of which the modification date is used, not 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, not null

date - the date reference, not 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, not 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