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org.apache.commons.io
Class FileUtils

java.lang.Object
  |
  +--org.apache.commons.io.FileUtils
public class FileUtils
extends java.lang.Object

General file manipulation utilities.

Facilities are provided in the following areas:

Origin of code: Excalibur, Alexandria, Commons-Utils

Version:
$Id: FileUtils.java 293019 2005-10-01 19:52:29Z scolebourne $
Author:
Kevin A. Burton, Scott Sanders, Daniel Rall, Christoph.Reck, Peter Donald, Jeff Turner, Matthew Hawthorne, Jeremias Maerki, Stephen Colebourne, Ian Springer, Chris Eldredge

Field Summary
static java.io.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 java.lang.String byteCountToDisplaySize(long size)
          Returns a human-readable version of the file size (original is in bytes).
static void cleanDirectory(java.io.File directory)
          Clean a directory without deleting it.
private static void cleanDirectoryOnExit(java.io.File directory)
          Clean a directory without deleting it.
static boolean contentEquals(java.io.File file1, java.io.File file2)
          Compare the contents of two files to determine if they are equal or not.
static java.io.File[] convertFileCollectionToFileArray(java.util.Collection files)
          Converts a Collection containing java.io.File instanced into array representation.
static void copyDirectory(java.io.File srcDir, java.io.File destDir)
          Copies a whole directory to a new location preserving the file dates.
static void copyDirectory(java.io.File srcDir, java.io.File destDir, boolean preserveFileDate)
          Copies a whole directory to a new location.
static void copyFile(java.io.File srcFile, java.io.File destFile)
          Copies a file to a new location preserving the file date.
static void copyFile(java.io.File srcFile, java.io.File destFile, boolean preserveFileDate)
          Copies a file to a new location.
static void copyFileToDirectory(java.io.File srcFile, java.io.File destDir)
          Copies a file to a directory preserving the file date.
static void copyURLToFile(java.net.URL source, java.io.File destination)
          Copies bytes from the URL source to a file destination.
static void deleteDirectory(java.io.File directory)
          Recursively delete a directory.
private static void deleteDirectoryOnExit(java.io.File directory)
          Recursively schedule directory for deletion on JVM exit.
private static void doCopyDirectory(java.io.File srcDir, java.io.File destDir, boolean preserveFileDate)
          Internal copy directory method.
private static void doCopyFile(java.io.File srcFile, java.io.File destFile, boolean preserveFileDate)
          Internal copy file method.
static void forceDelete(java.io.File file)
           Delete a file.
static void forceDeleteOnExit(java.io.File file)
          Schedule a file to be deleted when JVM exits.
static void forceMkdir(java.io.File directory)
          Make a directory, including any necessary but nonexistent parent directories.
private static void innerListFiles(java.util.Collection files, java.io.File directory, IOFileFilter filter)
          Finds files within a given directory (and optionally its subdirectories).
static boolean isFileNewer(java.io.File file, java.util.Date date)
          Tests if the specified File is newer than the specified Date.
static boolean isFileNewer(java.io.File file, java.io.File reference)
          Tests if the specified File is newer than the reference File.
static boolean isFileNewer(java.io.File file, long timeMillis)
          Tests if the specified File is newer than the specified time reference.
static java.util.Collection listFiles(java.io.File directory, IOFileFilter fileFilter, IOFileFilter dirFilter)
          Finds files within a given directory (and optionally its subdirectories).
static java.util.Collection listFiles(java.io.File directory, java.lang.String[] extensions, boolean recursive)
          Finds files within a given directory (and optionally its subdirectories) which match an array of extensions.
static byte[] readFileToByteArray(java.io.File file)
           Reads the contents of a file into a byte array.
static java.lang.String readFileToString(java.io.File file, java.lang.String encoding)
           Reads the contents of a file into a String.
static java.util.List readLines(java.io.File file, java.lang.String encoding)
           Reads the contents of a file line by line to a List of Strings.
static long sizeOfDirectory(java.io.File directory)
          Recursively count size of a directory (sum of the length of all files).
static java.io.File toFile(java.net.URL url)
          Convert from a URL to a File.
static java.io.File[] toFiles(java.net.URL[] urls)
          Converts each of an array of URL to a File.
private static java.lang.String[] toSuffixes(java.lang.String[] extensions)
          Converts an array of file extensions to suffixes for use with IOFileFilters.
static void touch(java.io.File file)
          Implements the same behaviour as the "touch" utility on Unix.
static java.net.URL[] toURLs(java.io.File[] files)
          Converts each of an array of File to a URL.
static boolean waitFor(java.io.File file, int seconds)
          Waits for NFS to propagate a file creation, imposing a timeout.
static void writeByteArrayToFile(java.io.File file, byte[] data)
           Writes a byte array to a file creating the file if it does not exist.
static void writeLines(java.io.File file, java.lang.String encoding, java.util.Collection lines)
           Writes the toString() value of each item in a collection to the specified File line by line.
static void writeLines(java.io.File file, java.lang.String encoding, java.util.Collection lines, java.lang.String lineEnding)
           Writes the toString() value of each item in a collection to the specified File line by line.
static void writeStringToFile(java.io.File file, java.lang.String data, java.lang.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, registerNatives, toString, wait, wait, wait
 

Field Detail

ONE_KB

public static final long ONE_KB
The number of bytes in a kilobyte.

ONE_MB

public static final long ONE_MB
The number of bytes in a megabyte.

ONE_GB

public static final long ONE_GB
The number of bytes in a gigabyte.

EMPTY_FILE_ARRAY

public static final java.io.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 java.lang.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(java.io.File file)
                  throws java.io.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:
java.io.IOException - If an I/O problem occurs

innerListFiles

private static void innerListFiles(java.util.Collection files,
                                   java.io.File directory,
                                   IOFileFilter filter)

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

Parameters:
files - the collection of files found.
directory - the directory to search in.
filter - the filter to apply to files and directories.

convertFileCollectionToFileArray

public static java.io.File[] convertFileCollectionToFileArray(java.util.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 java.util.Collection listFiles(java.io.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

toSuffixes

private static java.lang.String[] toSuffixes(java.lang.String[] extensions)
Converts an array of file extensions to suffixes for use with IOFileFilters.
Parameters:
extensions - an array of extensions. Format: {"java", "xml"}
Returns:
an array of suffixes. Format: {".java", ".xml"}

listFiles

public static java.util.Collection listFiles(java.io.File directory,
                                             java.lang.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(java.io.File file1,
                                    java.io.File file2)
                             throws java.io.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:
java.io.IOException - in case of an I/O error

toFile

public static java.io.File toFile(java.net.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:
java.lang.IllegalArgumentException - if the file is incorrectly encoded

toFiles

public static java.io.File[] toFiles(java.net.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:
java.lang.IllegalArgumentException - if any file is not a URL file
java.lang.IllegalArgumentException - if any file is incorrectly encoded
Since:
Commons IO 1.1

toURLs

public static java.net.URL[] toURLs(java.io.File[] files)
                             throws java.io.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:
java.io.IOException - if a file cannot be converted

copyFileToDirectory

public static void copyFileToDirectory(java.io.File srcFile,
                                       java.io.File destDir)
                                throws java.io.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
java.io.IOException - if source or destination is invalid
java.io.IOException - if an IO error occurs during copying
See Also:
copyFile(File, File, boolean)

copyFile

public static void copyFile(java.io.File srcFile,
                            java.io.File destFile)
                     throws java.io.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
java.io.IOException - if source or destination is invalid
java.io.IOException - if an IO error occurs during copying
See Also:
copyFileToDirectory(java.io.File, java.io.File)

copyFile

public static void copyFile(java.io.File srcFile,
                            java.io.File destFile,
                            boolean preserveFileDate)
                     throws java.io.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
java.io.IOException - if source or destination is invalid
java.io.IOException - if an IO error occurs during copying
See Also:
copyFileToDirectory(java.io.File, java.io.File)

doCopyFile

private static void doCopyFile(java.io.File srcFile,
                               java.io.File destFile,
                               boolean preserveFileDate)
                        throws java.io.IOException
Internal copy file method.
Parameters:
srcFile - the validated source file, not null
destFile - the validated destination file, not null
preserveFileDate - whether to preserve the file date
Throws:
java.io.IOException - if an error occurs

copyDirectory

public static void copyDirectory(java.io.File srcDir,
                                 java.io.File destDir)
                          throws java.io.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. If it already exists, the contents will be overwritten.

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
java.io.IOException - if source or destination is invalid
java.io.IOException - if an IO error occurs during copying
Since:
Commons IO 1.1

copyDirectory

public static void copyDirectory(java.io.File srcDir,
                                 java.io.File destDir,
                                 boolean preserveFileDate)
                          throws java.io.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
java.io.IOException - if source or destination is invalid
java.io.IOException - if an IO error occurs during copying
Since:
Commons IO 1.1

doCopyDirectory

private static void doCopyDirectory(java.io.File srcDir,
                                    java.io.File destDir,
                                    boolean preserveFileDate)
                             throws java.io.IOException
Internal copy directory method.
Parameters:
srcDir - the validated source directory, not null
destDir - the validated destination directory, not null
preserveFileDate - whether to preserve the file date
Throws:
java.io.IOException - if an error occurs
Since:
Commons IO 1.1

copyURLToFile

public static void copyURLToFile(java.net.URL source,
                                 java.io.File destination)
                          throws java.io.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:
java.io.IOException - if
  • source URL cannot be opened
  • destination cannot be written to
  • an IO error occurs during copying

deleteDirectory

public static void deleteDirectory(java.io.File directory)
                            throws java.io.IOException
Recursively delete a directory.
Parameters:
directory - directory to delete
Throws:
java.io.IOException - in case deletion is unsuccessful

cleanDirectory

public static void cleanDirectory(java.io.File directory)
                           throws java.io.IOException
Clean a directory without deleting it.
Parameters:
directory - directory to clean
Throws:
java.io.IOException - in case cleaning is unsuccessful

waitFor

public static boolean waitFor(java.io.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.

readFileToString

public static java.lang.String readFileToString(java.io.File file,
                                                java.lang.String encoding)
                                         throws java.io.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, null means platform default
Returns:
The file contents or null if read failed.
Throws:
java.io.IOException - in case of an I/O error
java.io.UnsupportedEncodingException - if the encoding is not supported by the VM

readFileToByteArray

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

Reads the contents of a file into a byte array.

Parameters:
file - the file to read
Returns:
The file contents or null if read failed.
Throws:
java.io.IOException - in case of an I/O error
Since:
Commons IO 1.1

readLines

public static java.util.List readLines(java.io.File file,
                                       java.lang.String encoding)
                                throws java.io.IOException

Reads the contents of a file line by line to a List of Strings.

There is no readLines 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, null means platform default
Returns:
the list of Strings representing each line in the file
Throws:
java.io.IOException - in case of an I/O error
java.io.UnsupportedEncodingException - if the encoding is not supported by the VM
Since:
Commons IO 1.1

writeStringToFile

public static void writeStringToFile(java.io.File file,
                                     java.lang.String data,
                                     java.lang.String encoding)
                              throws java.io.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 therefore results in 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:
java.io.IOException - in case of an I/O error
java.io.UnsupportedEncodingException - if the encoding is not supported by the VM

writeByteArrayToFile

public static void writeByteArrayToFile(java.io.File file,
                                        byte[] data)
                                 throws java.io.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:
java.io.IOException - in case of an I/O error
Since:
Commons IO 1.1

writeLines

public static void writeLines(java.io.File file,
                              java.lang.String encoding,
                              java.util.Collection lines)
                       throws java.io.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 therefore results in 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:
java.io.IOException - in case of an I/O error
java.io.UnsupportedEncodingException - if the encoding is not supported by the VM
Since:
Commons IO 1.1

writeLines

public static void writeLines(java.io.File file,
                              java.lang.String encoding,
                              java.util.Collection lines,
                              java.lang.String lineEnding)
                       throws java.io.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 therefore results in 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:
java.io.IOException - in case of an I/O error
java.io.UnsupportedEncodingException - if the encoding is not supported by the VM
Since:
Commons IO 1.1

forceDelete

public static void forceDelete(java.io.File file)
                        throws java.io.IOException

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

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

Parameters:
file - file or directory to delete.
Throws:
java.io.IOException - in case deletion is unsuccessful

forceDeleteOnExit

public static void forceDeleteOnExit(java.io.File file)
                              throws java.io.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:
java.io.IOException - in case deletion is unsuccessful

deleteDirectoryOnExit

private static void deleteDirectoryOnExit(java.io.File directory)
                                   throws java.io.IOException
Recursively schedule directory for deletion on JVM exit.
Parameters:
directory - directory to delete.
Throws:
java.io.IOException - in case deletion is unsuccessful

cleanDirectoryOnExit

private static void cleanDirectoryOnExit(java.io.File directory)
                                  throws java.io.IOException
Clean a directory without deleting it.
Parameters:
directory - directory to clean.
Throws:
java.io.IOException - in case cleaning is unsuccessful

forceMkdir

public static void forceMkdir(java.io.File directory)
                       throws java.io.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
Throws:
java.io.IOException - if the directory cannot be created.

sizeOfDirectory

public static long sizeOfDirectory(java.io.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, 0 if directory is security restricted

isFileNewer

public static boolean isFileNewer(java.io.File file,
                                  java.io.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.
Returns:
true if the File exists and has been modified more recently than the reference File.

isFileNewer

public static boolean isFileNewer(java.io.File file,
                                  java.util.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(java.io.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.
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