org.apache.commons.io
Class FilenameUtils

java.lang.Object
  extended by org.apache.commons.io.FilenameUtils

public class FilenameUtils
extends Object

General filename and filepath manipulation utilities.

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.

NOTE: You may be able to avoid using this class entirely simply by using JDK File objects and the two argument constructor File(File,String).

Most methods on this class are designed to work the same on both Unix and Windows. Those that don't include 'System', 'Unix' or 'Windows' in their name.

Most methods recognise both separators (forward and back), and both sets of prefixes. See the javadoc of each method for details.

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

Note that this class works best if directory filenames end with a separator. If you omit the last separator, it is impossible to determine if the filename corresponds to a file or a directory. As a result, we have chosen to say it corresponds to a file.

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

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

Origin of code: Excalibur, Alexandria, Tomcat, Commons-Utils.

Since:
Commons IO 1.1
Version:
$Id: FilenameUtils.java 609870 2008-01-08 04:46:26Z niallp $
Author:
Kevin A. Burton, Scott Sanders, Daniel Rall, Christoph.Reck, Peter Donald, Jeff Turner, Matthew Hawthorne, Martin Cooper, Jeremias Maerki, Stephen Colebourne

Field Summary
static char EXTENSION_SEPARATOR
          The extension separator character.
static String EXTENSION_SEPARATOR_STR
          The extension separator String.
 
Constructor Summary
FilenameUtils()
          Instances should NOT be constructed in standard programming.
 
Method Summary
static String concat(String basePath, String fullFilenameToAdd)
          Concatenates a filename to a base path using normal command line style rules.
static boolean equals(String filename1, String filename2)
          Checks whether two filenames are equal exactly.
static boolean equals(String filename1, String filename2, boolean normalized, IOCase caseSensitivity)
          Checks whether two filenames are equal, optionally normalizing and providing control over the case-sensitivity.
static boolean equalsNormalized(String filename1, String filename2)
          Checks whether two filenames are equal after both have been normalized.
static boolean equalsNormalizedOnSystem(String filename1, String filename2)
          Checks whether two filenames are equal after both have been normalized and using the case rules of the system.
static boolean equalsOnSystem(String filename1, String filename2)
          Checks whether two filenames are equal using the case rules of the system.
static String getBaseName(String filename)
          Gets the base name, minus the full path and extension, from a full filename.
static String getExtension(String filename)
          Gets the extension of a filename.
static String getFullPath(String filename)
          Gets the full path from a full filename, which is the prefix + path.
static String getFullPathNoEndSeparator(String filename)
          Gets the full path from a full filename, which is the prefix + path, and also excluding the final directory separator.
static String getName(String filename)
          Gets the name minus the path from a full filename.
static String getPath(String filename)
          Gets the path from a full filename, which excludes the prefix.
static String getPathNoEndSeparator(String filename)
          Gets the path from a full filename, which excludes the prefix, and also excluding the final directory separator.
static String getPrefix(String filename)
          Gets the prefix from a full filename, such as C:/ or ~/.
static int getPrefixLength(String filename)
          Returns the length of the filename prefix, such as C:/ or ~/.
static int indexOfExtension(String filename)
          Returns the index of the last extension separator character, which is a dot.
static int indexOfLastSeparator(String filename)
          Returns the index of the last directory separator character.
static boolean isExtension(String filename, Collection extensions)
          Checks whether the extension of the filename is one of those specified.
static boolean isExtension(String filename, String extension)
          Checks whether the extension of the filename is that specified.
static boolean isExtension(String filename, String[] extensions)
          Checks whether the extension of the filename is one of those specified.
static String normalize(String filename)
          Normalizes a path, removing double and single dot path steps.
static String normalizeNoEndSeparator(String filename)
          Normalizes a path, removing double and single dot path steps, and removing any final directory separator.
static String removeExtension(String filename)
          Removes the extension from a filename.
static String separatorsToSystem(String path)
          Converts all separators to the system separator.
static String separatorsToUnix(String path)
          Converts all separators to the Unix separator of forward slash.
static String separatorsToWindows(String path)
          Converts all separators to the Windows separator of backslash.
static boolean wildcardMatch(String filename, String wildcardMatcher)
          Checks a filename to see if it matches the specified wildcard matcher, always testing case-sensitive.
static boolean wildcardMatch(String filename, String wildcardMatcher, IOCase caseSensitivity)
          Checks a filename to see if it matches the specified wildcard matcher allowing control over case-sensitivity.
static boolean wildcardMatchOnSystem(String filename, String wildcardMatcher)
          Checks a filename to see if it matches the specified wildcard matcher using the case rules of the system.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

EXTENSION_SEPARATOR

public static final char EXTENSION_SEPARATOR
The extension separator character.

Since:
Commons IO 1.4
See Also:
Constant Field Values

EXTENSION_SEPARATOR_STR

public static final String EXTENSION_SEPARATOR_STR
The extension separator String.

Since:
Commons IO 1.4
Constructor Detail

FilenameUtils

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

Method Detail

normalize

public static String normalize(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 retained. 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/..           -->   foo/
 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 filename, or null if invalid

normalizeNoEndSeparator

public static String normalizeNoEndSeparator(String filename)
Normalizes a path, removing double and single dot path steps, and removing any final directory separator.

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/..           -->   foo
 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 filename, or null if invalid

concat

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

The effect is equivalent to resultant directory after changing directory to the first argument, followed by changing directory to the second argument.

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 an absolute 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 + bar           -->   /foo/bar
 /foo + /bar          -->   /bar
 /foo + C:/bar        -->   C:/bar
 /foo + C:bar         -->   C:bar (*)
 /foo/a/ + ../bar     -->   foo/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 Windows relative drive prefix is unreliable when used with this method. (!) 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 String separatorsToUnix(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 String separatorsToWindows(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 String separatorsToSystem(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(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 length includes the first slash in the full filename if applicable. Thus, it is possible that the length returned is greater than the length of the input string.

 Windows:
 a\b\c.txt           --> ""          --> relative
 \a\b\c.txt          --> "\"         --> current drive absolute
 C:a\b\c.txt         --> "C:"        --> 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
 ~                   --> "~/"        --> current user (slash added)
 ~user/a/b/c.txt     --> "~user/"    --> named user
 ~user               --> "~user/"    --> named user (slash added)
 

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(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(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 String getPrefix(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 where applicable.

 Windows:
 a\b\c.txt           --> ""          --> relative
 \a\b\c.txt          --> "\"         --> current drive absolute
 C:a\b\c.txt         --> "C:"        --> 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
 ~                   --> "~/"        --> current user (slash added)
 ~user/a/b/c.txt     --> "~user/"    --> named user
 ~user               --> "~user/"    --> named user (slash added)
 

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 String getPath(String filename)
Gets the path from a full filename, which excludes the prefix.

This method will handle a file in either Unix or Windows format. The method is entirely text based, and returns the text before and including the last forward or backslash.

 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.

This method drops the prefix from the result. See getFullPath(String) for the method that retains the prefix.

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

getPathNoEndSeparator

public static String getPathNoEndSeparator(String filename)
Gets the path from a full filename, which excludes the prefix, and also excluding the final directory separator.

This method will handle a file in either Unix or Windows format. The method is entirely text based, and returns the text before the last forward or backslash.

 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.

This method drops the prefix from the result. See getFullPathNoEndSeparator(String) for the method that retains the prefix.

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 String getFullPath(String filename)
Gets the full path from a full filename, which is the prefix + path.

This method will handle a file in either Unix or Windows format. The method is entirely text based, and returns the text before and including the last forward or backslash.

 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/
 C:           --> C:
 C:\          --> C:\
 ~            --> ~/
 ~/           --> ~/
 ~user        --> ~user/
 ~user/       --> ~user/
 

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

getFullPathNoEndSeparator

public static String getFullPathNoEndSeparator(String filename)
Gets the full path from a full filename, which is the prefix + path, and also excluding the final directory separator.

This method will handle a file in either Unix or Windows format. The method is entirely text based, and returns the text before the last forward or backslash.

 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
 C:           --> C:
 C:\          --> C:\
 ~            --> ~
 ~/           --> ~
 ~user        --> ~user
 ~user/       --> ~user
 

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 String getName(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 String getBaseName(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 String getExtension(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 String removeExtension(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(String filename1,
                             String filename2)
Checks whether two filenames are equal exactly.

No processing is performed on the filenames other than comparison, thus this is merely a null-safe case-sensitive equals.

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
See Also:
IOCase.SENSITIVE

equalsOnSystem

public static boolean equalsOnSystem(String filename1,
                                     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
See Also:
IOCase.SYSTEM

equalsNormalized

public static boolean equalsNormalized(String filename1,
                                       String filename2)
Checks whether two filenames are equal after both have been normalized.

Both filenames are first passed to normalize(String). The check is then performed in a case-sensitive manner.

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
See Also:
IOCase.SENSITIVE

equalsNormalizedOnSystem

public static boolean equalsNormalizedOnSystem(String filename1,
                                               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
See Also:
IOCase.SYSTEM

equals

public static boolean equals(String filename1,
                             String filename2,
                             boolean normalized,
                             IOCase caseSensitivity)
Checks whether two filenames are equal, optionally normalizing and providing control over the case-sensitivity.

Parameters:
filename1 - the first filename to query, may be null
filename2 - the second filename to query, may be null
normalized - whether to normalize the filenames
caseSensitivity - what case sensitivity rule to use, null means case-sensitive
Returns:
true if the filenames are equal, null equals null
Since:
Commons IO 1.3

isExtension

public static boolean isExtension(String filename,
                                  String extension)
Checks whether the extension of the filename is that specified.

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 all platforms.

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(String filename,
                                  String[] extensions)
Checks whether the extension of the filename is one of those specified.

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 all platforms.

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(String filename,
                                  Collection extensions)
Checks whether the extension of the filename is one of those specified.

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 all platforms.

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(String filename,
                                    String wildcardMatcher)
Checks a filename to see if it matches the specified wildcard matcher, always testing case-sensitive.

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 check is case-sensitive always.

 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
See Also:
IOCase.SENSITIVE

wildcardMatchOnSystem

public static boolean wildcardMatchOnSystem(String filename,
                                            String wildcardMatcher)
Checks a filename to see if it matches the specified wildcard matcher using the case rules of the system.

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 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
See Also:
IOCase.SYSTEM

wildcardMatch

public static boolean wildcardMatch(String filename,
                                    String wildcardMatcher,
                                    IOCase caseSensitivity)
Checks a filename to see if it matches the specified wildcard matcher allowing control over case-sensitivity.

The wildcard matcher uses the characters '?' and '*' to represent a single or multiple wildcard characters.

Parameters:
filename - the filename to match on
wildcardMatcher - the wildcard string to match against
caseSensitivity - what case sensitivity rule to use, null means case-sensitive
Returns:
true if the filename matches the wilcard string
Since:
Commons IO 1.3


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