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javafilenullpointerexceptionnosuchfileexception

Java isn't getting the file in the source code when compiled

Recently I have an issue with Java. I've tried some things I found on the web but they haven't worked, so I need help. I have a Java project in Eclipse. My main class is in src/programCode/UI_Main2.java. In that .java I try to access to a file in src/files/File.file

And this is when the things fo weird.

  • If I use /src/files/File.file it gives me NoSuchFileException.

  • If I use src/files/File.file it works in Eclipse but when I compile it to a executable .jar it gives me NoSuchFileException.

  • If I use /files/File.file it gives me NoSuchFileException.

  • If I use files/File.file it gives me NoSuchFileException.

  • If I use files/File.file it gives meNoSuchFileException.

  • If I use this.getClass().getResource("/files/File.file").getPath().substring(1) (without substring it gives me Invalid character) it gives me NoSuchFileException (but it shows me the absolute path and the file exists there!)

  • If I use this.getClass().getResource("files/File.file").getPath() it gives me NullPointerException and the program crashes.

  • If I use this.getClass().getResource("src/files/File.file").getPath() it gives me NullPointerException and the program crashes.

  • If I use this.getClass().getResource("/src/files/File.file").getPath() it gives me NullPointerException and the program crashes.

So, I don't know what to do. src/files/File.file is the only one that works, but it doesn't when compiled to executable jar. So please, help me, I haven't found any solution yet. Thanks!

Solution

  • Finding a file depends on two things:

    • Whether you use absolute or relative path
    • Where is your working directory

    Under Unix-like system when you use path like /dir1/dir2/file you use absolute path, so your working directory doesn't matter, but you must have a file exactly under that path.

    In your case you try to use relative path, so you shouldn't use / at the beginning.

    This case is crucial to your problem:

    "If I use src/files/File.file it works in Eclipse but when I compile it to a executable .jar it gives me NoSuchFileException."

    By default Eclipse uses as working directory a parent directory of src (which is usually a direcotry with your project", so starting from there you indeed have a file under that path.

    When you start a .jar your working directory is somewhere else. Put your .jar to parent directory of src and it should work.

    Now, I suggest that you change location of the file to a directory other than src (call it Resurces or something) and provide it along with the .jar.

    Also, here is an interesting discussion about working directories and .jar files:

    Current working directory when running a Jar

    If you want to distribute a single .jar here is a good packaging instruction:

    http://www.cefns.nau.edu/~edo/Classes/CS477_WWW/Docs/pack_resources_in_jar.html