How does Java resolve a relative path in new File

Question

I am trying to understand the way Java resolves relative path in while creating a File object   OS used  Windows  For the below snippet  I am getting an IOException as it cannot find the path    Test public void testPathConversion             File f   new File  test test txt            try               f createNewFile                System out println f getPath                 System out println f getAbsolutePath                     System out println f getCanonicalPath               catch  Exception e                e printStackTrace                  My understanding here is  Java treats the path provided as absolute and returns an error when the path does not exist  So it makes sense   When I update the above code to use relative path       Test     public void testPathConversion             File f   new File  test    test txt            try               f createNewFile                System out println f getPath                 System out println f getAbsolutePath                     System out println f getCanonicalPath               catch  Exception e                e printStackTrace                          It creates a new file and provides the below output   test    test txt C  JavaForTesters test    test txt C  JavaForTesters test txt   In this case  my assumption is  even though the path provided doesn t exist  because the path contains         java treats this as a relative path and creates the file in the user dir   So this also makes sense   But if I update the relative path as below       Test     public void testPathConversion             File f   new File  test       test txt            try               f createNewFile                System out println f getPath                 System out println f getAbsolutePath                 System out println f getCanonicalPath               catch  Exception e                e printStackTrace                      Then I get IOException  Access is denied   My questions are    why  test    test txt  is treated as a relative path and creates the file in  user dir  but test       test txt  returns an error  Where does it attempt to create the file for the path  test       test txt   When the specified relative path is not found  the file seems to be created in the user dir  So  it appears to me that the below two scenarios does the same thing     scenario 1 File f   new File  test    test txt    f createNewFile       scenario 2 File f   new File  test txt    f createNewFile       So is there a real world case where one would use scenario 1 instead of scenario 2    I suppose I am missing something obvious here or have fundamentally misunderstood relative paths  I went through the Java docs for File and I am not able to find an explanation for this  There are quite a few questions posted in Stack Overflow regarding relative paths  but the ones I looked up were for specific scenarios and not exactly about how relative paths are resolved    It will be great if someone could please explain me how this works or point to some related links

User · Accepted Answer

There is a concept of a working directory  This directory is represented by a    dot   In relative paths  everything else is relative to it   Simply put the    the working directory  is where you run your program   In some cases the working directory can be changed but in general this is   what the dot represents  I think this is C  JavaForTesters  in your case   So test    test txt means  the sub-directory test  in my working directory  then one level up  then the  file test txt  This is basically the same as just test txt   For more details check here   http   docs oracle com javase 7 docs api java io File html  http   docs oracle com javase tutorial essential io pathOps html

User · Answer

Relative paths can be best understood if you know how Java runs the program    There is a concept of working directory when running programs in Java  Assuming you have a class  say  FileHelper that does the IO under   User home Desktop projectRoot src topLevelPackage     Depending on the case where you invoke java to run the program  you will have different working directory  If you run your program from within and IDE  it will most probably be projectRoot    In this case   projectRoot src   java topLevelPackage FileHelper it will be src  In this case   projectRoot   java -cp src topLevelPackage FileHelper it will be projectRoot  In this case    User home Desktop   java -cp   projectRoot src topLevelPackage FileHelper it will be Desktop     Assuming   is your command prompt with standard Unix-like FileSystem  Similar correspondence parallels with Windows system   So  your relative path root     resolves to your working directory  Thus to be better sure of where to write files  it s said to consider below approach   package topLevelPackage  import java io File  import java nio file Path  import java nio file Paths   public class FileHelper           Not full implementation  just barebone stub for path     public void createLocalFile                 Explicitly get hold of working directory         String workingDir   System getProperty  user dir             Path filePath   Paths get workingDir File separator  sampleFile txt                In case we need specific path  traverse that path  rather using   or             Path pathToProjectRoot   Paths get System getProperty  user home     Desktop    projectRoot             System out println filePath           System out println pathToProjectRoot              Hope this helps

User · Answer

When your path starts with a root dir i e  C   in windows or   in Unix or in java resources path  it is considered to be an absolute path  Everything else is relative  so   new File  test txt   is the same as new File    test txt    new File  test    test txt   is the same as new File    test    test txt     The major difference between getAbsolutePath and getCanonicalPath is that the first one concatenates a parent and a child path  so it may contain dots     or    getCanonicalPath will always return the same path for a particular file   Note  File equals uses an abstract form of a path  getAbsolutePath  to compare files  so this means that two File objects for the same might not be equal and Files are unsafe to use in collections like Map or Set

User · Answer

Only slightly related to the question  but try to wrap your head around this one   So un-intuitive   import java nio file    class Main     public static void main String   args        Path p1   Paths get   personal   photos   readme txt        Path p2   Paths get   personal index html        Path p3   p1 relativize p2       System out println p3     prints              index html

User · Answer

On windows and Netbeans you can set the relative path as       new FileReader  src  PACKAGE NAME  FILENAME      On Linux and Netbeans you can set the relative path as       new FileReader  src PACKAGE NAME FILENAME      If you have your code inside Source Packages I do not know if it is the same for eclipse or other IDE

User · Answer

I went off of peter petrov s answer but let me explain where you make the file edits to change it to a relative path    Simply edit  AXLAPIService java  and change   url   new URL  file C users     schema current AXLAPI wsdl     to   url   new URL  file   schema current AXLAPI wsdl     or where ever you want to store it    You can still work on packaging the wsdl file into the meta-inf folder in the jar but this was the simplest way to get it working for me

User · Answer

The working directory is a common concept across virtually all operating systems and program languages etc  It s the directory in which your program is running  This is usually  but not always  there are ways to change it  the directory the application is in   Relative paths are ones that start without a drive specifier  So in linux they don t start with a    in windows they don t start with a C    etc  These always start from your working directory   Absolute paths are the ones that start with a drive  or machine for network paths  specifier  They always go from the start of that drive

[java] How does Java resolve a relative path in new File()?

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