org.apache.commons.io
Class FileUtils

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

public class FileUtils
extends Object

This class provides basic facilities for manipulating files and file paths.

Path-related methods

Methods exist to retrieve the components of a typical file path. For example /www/hosted/mysite/index.html, can be broken into:

• /www/hosted/mysite/ -- retrievable through #getPath
• index.html -- retrievable through #removePath
• /www/hosted/mysite/index -- retrievable through #removeExtension
• html -- retrievable through #getExtension

There are also methods to concatenate two paths, resolve a path relative to a File and #normalize a path.

File-related methods

There are methods to create a File from a URL, copy a File to a directory, copy a File to another File, copy a URL's contents to a File, as well as methods to delete and clean a directory.

Common File manipulation routines.

Origin of code

• commons-utils repo
• Alexandria's FileUtils.
• Avalon Excalibur's IO.

Version:

$Id: FileUtils.java 140562 2004-04-24 19:46:16Z jeremias $

Author:

Kevin A. Burton, Scott Sanders, Daniel Rall, Christoph.Reck, Peter Donald, Jeff Turner, Matthew Hawthorne, Jeremias Maerki

Field Summary

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 (original is in 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	copyFile(File source, File destination) Copy file from source to destination.
static void	copyFile(File source, File destination, boolean preserveFileDate) Copy file from source to destination.
static void	copyFileToDirectory(File source, File destinationDirectory) Copy file from source to destination.
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.
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 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 String	readFileToString(File file, String encoding) Reads the contents of a file into a String.
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 void	touch(File file) Implements the same behaviour as the "touch" utility on Unix.
static URL[]	toURLs(File[] files) Convert the array of Files into a list of URLs.
static boolean	waitFor(File file, int seconds) Waits for NFS to propagate a file creation, imposing a timeout.
static void	writeStringToFile(File file, String data, String encoding) Writes data to a file.

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

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 (original is in 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

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, too.

Returns:

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

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.

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.

Parameters:

url - File URL.

Returns:

The equivalent File object, or null if the URL's protocol is not file

toURLs

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

Convert the array of Files into a list of URLs.

Parameters:

files - the array of files

Returns:

the array of URLs

Throws:

IOException - if an error occurs

copyFileToDirectory

public static void copyFileToDirectory(File source,
                                       File destinationDirectory)
                                throws IOException

Copy file from source to destination. If destinationDirectory does not exist, it (and any parent directories) will be created. If a file source in destinationDirectory exists, it will be overwritten. The copy will have the same file date as the original.

Parameters:

source - An existing File to copy.

destinationDirectory - A directory to copy source into.

Throws:

FileNotFoundException - if source isn't a normal file.

IllegalArgumentException - if destinationDirectory isn't a directory.

IOException - if source does not exist, the file in destinationDirectory cannot be written to, or an IO error occurs during copying.

copyFile

public static void copyFile(File source,
                            File destination)
                     throws IOException

Copy file from source to destination. The directories up to destination will be created if they don't already exist. destination will be overwritten if it already exists. The copy will have the same file date as the original.

Parameters:

source - An existing non-directory File to copy bytes from.

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

Throws:

IOException - if source does not exist, destination cannot be written to, or an IO error occurs during copying.

FileNotFoundException - if destination is a directory (use copyFileToDirectory(java.io.File, java.io.File)).

copyFile

public static void copyFile(File source,
                            File destination,
                            boolean preserveFileDate)
                     throws IOException

Copy file from source to 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 - An existing non-directory File to copy bytes from.

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

preserveFileDate - True if the file date of the copy should be the same as the original.

Throws:

IOException - if source does not exist, destination cannot be written to, or an IO error occurs during copying.

FileNotFoundException - if destination is a directory (use copyFileToDirectory(java.io.File, java.io.File)).

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.

Parameters:

file - The file

seconds - The maximum time in seconds to wait.

Returns:

True if file exists. TODO Needs a clearer javadoc to see its real purpose for someone without NFS-knowledge.

readFileToString

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

Reads the contents of a file into a String.

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

Parameters:

file - the file to read.

encoding - the encoding to use

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

writeStringToFile

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

Writes data to a file. The file will be created if it does not exist.

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

Parameters:

file - the file to write.

data - The content to write to the file.

encoding - encoding to use

Throws:

IOException - in case of an I/O error

UnsupportedEncodingException - if the encoding is not supported by the VM

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.

Throws:

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.

Throws:

IOException - in case deletion is unsuccessful

forceMkdir

public static void forceMkdir(File directory)
                       throws IOException

Make a directory. 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

Throws:

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

Returns:

size of directory in bytes.

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

reference - the File of which the modification date is used like reference

Returns:

true if the File exists and has been modified more recently than the reference File.

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

date - the date reference

Returns:

true if the File exists and has been modified after the given Date.

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.

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.