What s the difference between getPath getAbsolutePath and getCanonicalPath in Java

Question

What s the difference between getPath    getAbsolutePath    and getCanonicalPath   in Java   And when do I use each one

User · Answer

The best way I have found to get a feel for things like this is to try them out:

import java.io.File;
public class PathTesting {
    public static void main(String [] args) {
        File f = new File("test/.././file.txt");
        System.out.println(f.getPath());
        System.out.println(f.getAbsolutePath());
        try {
            System.out.println(f.getCanonicalPath());
        }
        catch(Exception e) {}
    }
}

Your output will be something like:

test\..\.\file.txt
C:\projects\sandbox\trunk\test\..\.\file.txt
C:\projects\sandbox\trunk\file.txt

So, getPath() gives you the path based on the File object, which may or may not be relative; getAbsolutePath() gives you an absolute path to the file; and getCanonicalPath() gives you the unique absolute path to the file. Notice that there are a huge number of absolute paths that point to the same file, but only one canonical path.

When to use each? Depends on what you're trying to accomplish, but if you were trying to see if two Files are pointing at the same file on disk, you could compare their canonical paths. Just one example.

User · Answer

getPath   returns the path used to create the File object  This return value is not changed based on the location it is run  results below are for windows  separators are obviously different elsewhere   File f1   new File   some path    String path   f1 getPath       will return   some path   File dir   new File   basedir    File f2   new File dir    some path    path   f2 getPath       will return   basedir some path   File f3   new File    some path    path   f3 getPath       will return    some path    getAbsolutePath   will resolve the path based on the execution location or drive  So if run from c  test   path   f1 getAbsolutePath       will return  c  some path  path   f2 getAbsolutePath       will return  c  basedir some path  path   f3 getAbsolutePath       will return  c  test   basedir some path    getCanonicalPath   is system dependent  It will resolve the unique location the path represents  So if you have any    s in the path they will typically be removed   As to when to use them  It depends on what you are trying to achieve  getPath   is useful for portability  getAbsolutePath   is useful to find the file system location  and getCanonicalPath   is particularly useful to check if two files are the same

User · Answer

Consider these filenames   C  temp file txt - This is a path  an absolute path  and a canonical path     file txt - This is a path  It s neither an absolute path nor a canonical path   C  temp myapp bin        file txt - This is a path and an absolute path  It s not a canonical path   A canonical path is always an absolute path   Converting from a path to a canonical path makes it absolute  usually tack on the current working directory so e g    file txt becomes c  temp file txt   The  canonical path of a file just  purifies  the path  removing and resolving stuff like     and resolving symlinks  on unixes    Also note the following example with nio Paths   String canonical path string    C   Windows  System32     String absolute path string    C   Windows  System32  drivers          System out println Paths get canonical path string  getParent     System out println Paths get absolute path string  getParent       While both paths refer to the same location  the output will be quite different   C  Windows C  Windows System32 drivers

User · Answer

I find I rarely have need to use getCanonicalPath   but  if given a File with a filename that is in DOS 8 3 format on Windows  such as the java io tmpdir System property returns  then this method will return the  full  filename

User · Answer

In short   getPath   gets the path string that the File object was constructed with  and it may be relative current directory  getAbsolutePath   gets the path string after resolving it against the current directory if it s relative  resulting in a fully qualified path  getCanonicalPath   gets the path string after resolving any relative path against current directory  and removes any relative pathing    and      and any file system links to return a path which the file system considers the canonical means to reference the file system object to which it points   Also  each of these has a File equivalent which returns the corresponding File object  Note that IMO  Java got the implementation of an  quot absolute quot  path wrong  it really should remove any relative path elements in an absolute path  The canonical form would then remove any FS links or junctions in the path

User · Answer

The big thing to get your head around is that the File class tries to represent a view of what Sun like to call  hierarchical pathnames   basically a path like c  foo txt or  usr muggins   This is why you create files in terms of paths  The operations you are describing are all operations upon this  pathname     getPath   fetches the path that the File was created with     foo txt  getAbsolutePath   fetches the path that the File was created with  but includes information about the current directory if the path is relative   usr bobstuff    foo txt  getCanonicalPath   attempts to fetch a unique representation of the absolute path to the file  This eliminates indirection from      and     references   usr foo txt     Note I say attempts - in forming a Canonical Path  the VM can throw an IOException  This usually occurs because it is performing some filesystem operations  any one of which could fail

[java] What's the difference between getPath(), getAbsolutePath(), and getCanonicalPath() in Java?

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