org.apache.commons.io
Class FilenameUtils

java.lang.Object
  extended byorg.apache.commons.io.FilenameUtils

public class FilenameUtils
extends java.lang.Object

Utility class that provides methods to manipulate filenames and filepaths.

When dealing with filenames you can hit problems when moving from a Windows based development machine to a Unix based production machine. This class aims to help avoid those problems.

Most methods on this class are designed to work the same on both Unix and Windows. Both separators (forward and back) are recognised, and both sets of prefixes. The comparison methods do differ by machine however, comparing case insensitive on Windows and case sensitive on Unix. See the javadoc of each method for details.

This class defines six components within a filename (example C:\dev\project\file.txt):

Note that the path of a directory is the parent directory.

This class only supports Unix and Windows style names. Prefixes are matched as follows:

 Windows style:
 a\b\c.txt           --> ""          --> relative
 \a\b\c.txt          --> "\"         --> drive relative
 C:\a\b\c.txt        --> "C:\"       --> absolute
 \\server\a\b\c.txt  --> "\\server\" --> UNC
 
 Unix style:
 a/b/c.txt           --> ""          --> relative
 /a/b/c.txt          --> "/"         --> absolute
 ~/a/b/c.txt         --> "~/"        --> current user relative
 ~user/a/b/c.txt     --> "~user/"    --> named user relative
 
Both prefix styles are matched always, irrespective of the machine that you are currently running on.

Origin of code

Since:
Commons IO 1.1
Version:
$Id: FilenameUtils.java,v 1.32 2004/12/10 22:36:56 scolebourne Exp $
Author:
Kevin A. Burton, Scott Sanders, Daniel Rall, Christoph.Reck, Peter Donald, Jeff Turner, Matthew Hawthorne, Martin Cooper, Jeremias Maerki, Stephen Colebourne

Field Summary
private static char EXTENSION_SEPARATOR
          The extension separator character.
private static char OTHER_SEPARATOR
          The separator character that is the opposite of the system separator.
private static char SYSTEM_SEPARATOR
          The system separator character.
private static char UNIX_SEPARATOR
          The Unix separator character.
private static char WINDOWS_SEPARATOR
          The Windows separator character.
 
Constructor Summary
FilenameUtils()
          Instances should NOT be constructed in standard programming.
 
Method Summary
static java.lang.String concat(java.lang.String basePath, java.lang.String fullFilenameToAdd)
          Concatenates a filename to a base path using normal command line style rules.
static boolean equals(java.lang.String filename1, java.lang.String filename2)
          Checks whether two filenames are equal using the case rules of the system.
static boolean equalsNormalized(java.lang.String filename1, java.lang.String filename2)
          Checks whether two filenames are equal after both have been normalized and using the case rules of the system.
static java.lang.String getBaseName(java.lang.String filename)
          Gets the base name, minus the full path and extension, from a full filename.
static java.lang.String getExtension(java.lang.String filename)
          Gets the extension of a filename.
static java.lang.String getFullPath(java.lang.String filename)
          Gets the full path from a full filename, which is the prefix + path.
static java.lang.String getName(java.lang.String filename)
          Gets the name minus the path from a full filename.
static java.lang.String getPath(java.lang.String filename)
          Gets the path from a full filename, which excludes the prefix.
static java.lang.String getPrefix(java.lang.String filename)
          Gets the prefix from a full filename, such as C:/ or ~/.
static int getPrefixLength(java.lang.String filename)
          Returns the length of the filename prefix, such as C:/ or ~/.
static int indexOfExtension(java.lang.String filename)
          Returns the index of the last extension separator character, which is a dot.
static int indexOfLastSeparator(java.lang.String filename)
          Returns the index of the last directory separator character.
static boolean isExtension(java.lang.String filename, java.util.Collection extensions)
          Checks whether the extension of the filename is one of those specified using the case rules of the system.
static boolean isExtension(java.lang.String filename, java.lang.String extension)
          Checks whether the extension of the filename is that specified using the case rules of the system.
static boolean isExtension(java.lang.String filename, java.lang.String[] extensions)
          Checks whether the extension of the filename is one of those specified using the case rules of the system.
private static boolean isSeparator(char ch)
          Checks if the character is a separator.
static java.lang.String normalize(java.lang.String filename)
          Normalizes a path, removing double and single dot path steps.
static java.lang.String removeExtension(java.lang.String filename)
          Removes the extension from a filename.
static java.lang.String separatorsToSystem(java.lang.String path)
          Converts all separators to the system separator.
static java.lang.String separatorsToUnix(java.lang.String path)
          Converts all separators to the Unix separator of forward slash.
static java.lang.String separatorsToWindows(java.lang.String path)
          Converts all separators to the Windows separator of backslash.
(package private) static java.lang.String[] splitOnTokens(java.lang.String text)
           
static boolean wildcardMatch(java.lang.String filename, java.lang.String wildcardMatcher)
          Checks a filename to see if it matches the specified wildcard matcher.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

EXTENSION_SEPARATOR

private static final char EXTENSION_SEPARATOR
The extension separator character.

See Also:
Constant Field Values

UNIX_SEPARATOR

private static final char UNIX_SEPARATOR
The Unix separator character.

See Also:
Constant Field Values

WINDOWS_SEPARATOR

private static final char WINDOWS_SEPARATOR
The Windows separator character.

See Also:
Constant Field Values

SYSTEM_SEPARATOR

private static final char SYSTEM_SEPARATOR
The system separator character.


OTHER_SEPARATOR

private static final char OTHER_SEPARATOR
The separator character that is the opposite of the system separator.

Constructor Detail

FilenameUtils

public FilenameUtils()
Instances should NOT be constructed in standard programming.

Method Detail

isSeparator

private static boolean isSeparator(char ch)
Checks if the character is a separator.

Parameters:
ch - the character to check
Returns:
true if it is a separator character

normalize

public static java.lang.String normalize(java.lang.String filename)
Normalizes a path, removing double and single dot path steps.

This method normalizes a path to a standard format. The input may contain separators in either Unix or Windows format. The output will contain separators in the format of the system.

A trailing slash will be removed. A double slash will be merged to a single slash (but UNC names are handled). A single dot path segment will be removed. A double dot will cause that path segment and the one before to be removed. If the double dot has no parent path segment to work with, null is returned.

The output will be the same on both Unix and Windows except for the separator character.

 /foo//               -->   /foo
 /foo/./              -->   /foo
 /foo/../bar          -->   /bar
 /foo/../bar/         -->   /bar
 /foo/../bar/../baz   -->   /baz
 //foo//./bar         -->   /foo/bar
 /../                 -->   null
 ../foo               -->   null
 foo/../../bar        -->   null
 foo/../bar           -->   bar
 //server/foo/../bar  -->   //server/bar
 //server/../bar      -->   null
 C:\foo\..\bar        -->   C:\bar
 C:\..\bar            -->   null
 ~/foo/../bar         -->   ~/bar
 ~/../bar             -->   null
 
(Note the file separator returned will be correct for Windows/Unix)

Parameters:
filename - the filename to normalize, null returns null
Returns:
the normalized String, or null if invalid

concat

public static java.lang.String concat(java.lang.String basePath,
                                      java.lang.String fullFilenameToAdd)
Concatenates a filename to a base path using normal command line style rules.

The first argument is the base path, the second is the path to concatenate. The returned path is always normalized via normalize(String), thus .. is handled.

If pathToAdd is absolute (has a prefix), then it will be normalized and returned. Otherwise, the paths will be joined, normalized and returned.

The output will be the same on both Unix and Windows except for the separator character.

 /foo/ + bar          -->   /foo/bar
 /foo/a + bar         -->   /foo/a/bar
 /foo/ + ../bar       -->   /bar
 /foo/ + ../../bar    -->   null
 /foo/ + /bar         -->   /bar
 /foo/.. + /bar       -->   /bar
 /foo + bar/c.txt     -->   /foo/bar/c.txt
 /foo/c.txt + bar     -->   /foo/c.txt/bar (!)
 
(!) Note that the first parameter must be a path. If it ends with a name, then the name will be built into the concatenated path. If this might be a problem, use getFullPath(String) on the base path argument.

Parameters:
basePath - the base path to attach to, always treated as a path
fullFilenameToAdd - the filename (or path) to attach to the base
Returns:
the concatenated path, or null if invalid

separatorsToUnix

public static java.lang.String separatorsToUnix(java.lang.String path)
Converts all separators to the Unix separator of forward slash.

Parameters:
path - the path to be changed, null ignored
Returns:
the updated path

separatorsToWindows

public static java.lang.String separatorsToWindows(java.lang.String path)
Converts all separators to the Windows separator of backslash.

Parameters:
path - the path to be changed, null ignored
Returns:
the updated path

separatorsToSystem

public static java.lang.String separatorsToSystem(java.lang.String path)
Converts all separators to the system separator.

Parameters:
path - the path to be changed, null ignored
Returns:
the updated path

getPrefixLength

public static int getPrefixLength(java.lang.String filename)
Returns the length of the filename prefix, such as C:/ or ~/.

This method will handle a file in either Unix or Windows format. The prefix includes the first slash in the full filename.

 Windows:
 a\b\c.txt           --> ""          --> relative
 \a\b\c.txt          --> "\"         --> drive relative
 C:\a\b\c.txt        --> "C:\"       --> absolute
 \\server\a\b\c.txt  --> "\\server\" --> UNC
 
 Unix:
 a/b/c.txt           --> ""          --> relative
 /a/b/c.txt          --> "/"         --> absolute
 ~/a/b/c.txt         --> "~/"        --> current user relative
 ~user/a/b/c.txt     --> "~user/"    --> named user relative
 

The output will be the same irrespective of the machine that the code is running on. ie. both Unix and Windows prefixes are matched regardless.

Parameters:
filename - the filename to find the prefix in, null returns -1
Returns:
the length of the prefix, -1 if invalid or null

indexOfLastSeparator

public static int indexOfLastSeparator(java.lang.String filename)
Returns the index of the last directory separator character.

This method will handle a file in either Unix or Windows format. The position of the last forward or backslash is returned.

The output will be the same irrespective of the machine that the code is running on.

Parameters:
filename - the filename to find the last path separator in, null returns -1
Returns:
the index of the last separator character, or -1 if there is no such character

indexOfExtension

public static int indexOfExtension(java.lang.String filename)
Returns the index of the last extension separator character, which is a dot.

This method also checks that there is no directory separator after the last dot. To do this it uses indexOfLastSeparator(String) which will handle a file in either Unix or Windows format.

The output will be the same irrespective of the machine that the code is running on.

Parameters:
filename - the filename to find the last path separator in, null returns -1
Returns:
the index of the last separator character, or -1 if there is no such character

getPrefix

public static java.lang.String getPrefix(java.lang.String filename)
Gets the prefix from a full filename, such as C:/ or ~/.

This method will handle a file in either Unix or Windows format. The prefix includes the first slash in the full filename.

 Windows:
 a\b\c.txt           --> ""          --> relative
 \a\b\c.txt          --> "\"         --> drive relative
 C:\a\b\c.txt        --> "C:\"       --> absolute
 \\server\a\b\c.txt  --> "\\server\" --> UNC
 
 Unix:
 a/b/c.txt           --> ""          --> relative
 /a/b/c.txt          --> "/"         --> absolute
 ~/a/b/c.txt         --> "~/"        --> current user relative
 ~user/a/b/c.txt     --> "~user/"    --> named user relative
 

The output will be the same irrespective of the machine that the code is running on. ie. both Unix and Windows prefixes are matched regardless.

Parameters:
filename - the filename to query, null returns null
Returns:
the prefix of the file, null if invalid

getPath

public static java.lang.String getPath(java.lang.String filename)
Gets the path from a full filename, which excludes the prefix. The path of a directory is the parent directory.

This method will handle a file in either Unix or Windows format. The text before the last forward or backslash is returned.

 C:\a\b\c.txt --> a\b
 ~/a/b/c.txt  --> a/b
 a.txt        --> ""
 a/b/c        --> a/b
 a/b/c/       --> a/b/c
 

The output will be the same irrespective of the machine that the code is running on.

Parameters:
filename - the filename to query, null returns null
Returns:
the path of the file, an empty string if none exists, null if invalid

getFullPath

public static java.lang.String getFullPath(java.lang.String filename)
Gets the full path from a full filename, which is the prefix + path. The path of a directory is the parent directory.

This method will handle a file in either Unix or Windows format. The text before the last forward or backslash is returned.

 C:\a\b\c.txt --> C:\a\b
 ~/a/b/c.txt  --> ~/a/b
 a.txt        --> ""
 a/b/c        --> a/b
 a/b/c/       --> a/b/c
 

The output will be the same irrespective of the machine that the code is running on.

Parameters:
filename - the filename to query, null returns null
Returns:
the path of the file, an empty string if none exists, null if invalid

getName

public static java.lang.String getName(java.lang.String filename)
Gets the name minus the path from a full filename.

This method will handle a file in either Unix or Windows format. The text after the last forward or backslash is returned.

 a/b/c.txt --> c.txt
 a.txt     --> a.txt
 a/b/c     --> c
 a/b/c/    --> ""
 

The output will be the same irrespective of the machine that the code is running on.

Parameters:
filename - the filename to query, null returns null
Returns:
the name of the file without the path, or an empty string if none exists

getBaseName

public static java.lang.String getBaseName(java.lang.String filename)
Gets the base name, minus the full path and extension, from a full filename.

This method will handle a file in either Unix or Windows format. The text after the last forward or backslash and before the last dot is returned.

 a/b/c.txt --> c
 a.txt     --> a
 a/b/c     --> c
 a/b/c/    --> ""
 

The output will be the same irrespective of the machine that the code is running on.

Parameters:
filename - the filename to query, null returns null
Returns:
the name of the file without the path, or an empty string if none exists

getExtension

public static java.lang.String getExtension(java.lang.String filename)
Gets the extension of a filename.

This method returns the textual part of the filename after the last dot. There must be no directory separator after the dot.

 foo.txt      --> "txt"
 a/b/c.jpg    --> "jpg"
 a/b.txt/c    --> ""
 a/b/c        --> ""
 

The output will be the same irrespective of the machine that the code is running on.

Parameters:
filename - the filename to retrieve the extension of.
Returns:
the extension of the file or an empty string if none exists.

removeExtension

public static java.lang.String removeExtension(java.lang.String filename)
Removes the extension from a filename.

This method returns the textual part of the filename before the last dot. There must be no directory separator after the dot.

 foo.txt    --> foo
 a\b\c.jpg  --> a\b\c
 a\b\c      --> a\b\c
 a.b\c      --> a.b\c
 

The output will be the same irrespective of the machine that the code is running on.

Parameters:
filename - the filename to query, null returns null
Returns:
the filename minus the extension

equals

public static boolean equals(java.lang.String filename1,
                             java.lang.String filename2)
Checks whether two filenames are equal using the case rules of the system.

No processing is performed on the filenames other than comparison. The check is case sensitive on Unix and case insensitive on Windows.

Parameters:
filename1 - the first filename to query, may be null
filename2 - the second filename to query, may be null
Returns:
true if the filenames are equal, null equals null

equalsNormalized

public static boolean equalsNormalized(java.lang.String filename1,
                                       java.lang.String filename2)
Checks whether two filenames are equal after both have been normalized and using the case rules of the system.

Both filenames are first passed to normalize(String). The check is then performed case sensitive on Unix and case insensitive on Windows.

Parameters:
filename1 - the first filename to query, may be null
filename2 - the second filename to query, may be null
Returns:
true if the filenames are equal, null equals null

isExtension

public static boolean isExtension(java.lang.String filename,
                                  java.lang.String extension)
Checks whether the extension of the filename is that specified using the case rules of the system.

This method obtains the extension as the textual part of the filename after the last dot. There must be no directory separator after the dot. The extension check is case sensitive on Unix and case insensitive on Windows.

Parameters:
filename - the filename to query, null returns false
extension - the extension to check for, null or empty checks for no extension
Returns:
true if the filename has the specified extension

isExtension

public static boolean isExtension(java.lang.String filename,
                                  java.lang.String[] extensions)
Checks whether the extension of the filename is one of those specified using the case rules of the system.

This method obtains the extension as the textual part of the filename after the last dot. There must be no directory separator after the dot. The extension check is case sensitive on Unix and case insensitive on Windows.

Parameters:
filename - the filename to query, null returns false
extensions - the extensions to check for, null checks for no extension
Returns:
true if the filename is one of the extensions

isExtension

public static boolean isExtension(java.lang.String filename,
                                  java.util.Collection extensions)
Checks whether the extension of the filename is one of those specified using the case rules of the system.

This method obtains the extension as the textual part of the filename after the last dot. There must be no directory separator after the dot. The extension check is case sensitive on Unix and case insensitive on Windows.

Parameters:
filename - the filename to query, null returns false
extensions - the extensions to check for, null checks for no extension
Returns:
true if the filename is one of the extensions

wildcardMatch

public static boolean wildcardMatch(java.lang.String filename,
                                    java.lang.String wildcardMatcher)
Checks a filename to see if it matches the specified wildcard matcher.

The wildcard matcher uses the characters '?' and '*' to represent a single or multiple wildcard characters. This is the same as often found on Dos/Unix command lines. The extension check is case sensitive on Unix and case insensitive on Windows.

 wildcardMatch("c.txt", "*.txt")      --> true
 wildcardMatch("c.txt", "*.jpg")      --> false
 wildcardMatch("a/b/c.txt", "a/b/*")  --> true
 wildcardMatch("c.txt", "*.???")      --> true
 wildcardMatch("c.txt", "*.????")     --> false
 

Parameters:
filename - the filename to match on
wildcardMatcher - the wildcard string to match against
Returns:
true if the filename matches the wilcard string

splitOnTokens

static java.lang.String[] splitOnTokens(java.lang.String text)