Why can't I read any of my resources in a jar file?

Question

For an application I was developing, I wanted to create a Binary File using the following code:
DataInputStream in = null;
        try {
            File file = new File(name);
            in = new DataInputStream(
                    new BufferedInputStream(
                        new FileInputStream(file)));
        } catch (FileNotFoundException e) {
            System.out.println("Non-existential File.");
            System.exit(0);
}I am using Netbeans 6.5.1., and it groups my projects so that there are folders for build, src, dist, nbproject inside the project folder. The application that I am developing is a graphics demo that requires the use of several text files to represent the maps, so I wanted to read them using a FileInputStream.
I kept this file, "islandmap.txt", in the src folder in my project. In the method above, I coded my program so that the "name" would be "src\islandmap.txt", and it read from the file perfectly. However, I needed to compile it to a Jar file too. After doing that, the program no longer functioned. I remembered when I used a tutorial long ago that used
URL url = getClass().getClassLoader().getResource(fileName) ... in order to get the directory of the files. That made sense, because a person who is running the program via Java Webstart or a Jar Executable would definitely not have the parts of the program located in the same directory, so the code is used to find where the java program is. However, I realized something...
File file = new File( - constructor - )There are four constructors for files, and I only think I could use two. The first is using a string, like I have done before with "src\islandmap.txt." Now, the URL url = getClass().getClassLoader().getResource(fileName) part, it was used before to locate a URL in order to open a buffered image. The constructor for File does not support URLs, but instead supports URIs.I tried converting between the two, changing a URL into a string, and producing a URI from the string. But it did not work, giving me an error that URI was not hierarchical. And that's when I realized that they were certainly not interchangable.
More specifically, here is my code as of now:
public boolean loadMap(String mapName) {
        String path = "src/islandmap.txt";   //This is where the map files are stored
        mapName = getClass().getClassLoader().getResource(path).getPath(); //getPath changes the URL into a String
        DataInputStream in = null;
        try {
            File file = new File(mapName);
            in = new DataInputStream(
                    new BufferedInputStream(
                        new FileInputStream(file)));
             //code to actually read from the file goes here
        } catch (FileNotFoundException e) {
            System.out.println("Non-existential File.");
            System.exit(0);
        } finally {
             //close in
}So that is my problem now. I am stuck. For my purposes, I basically must use a stored text file within my jar, but I don't know how to read it. It distresses me that normally, I already know how to open images that are located inside my src folder using URLs, but not any other file requiring a File class to be wrapped within a Buffered Writer/Reader. Could somebody please assist me with this, or suggest an alternative that would also fall under my conditions? I would appreciate it so much. Thank you.
Edited by: celestialsalt on Dec 6, 2009 5:29 PM
Edited by: celestialsalt on Dec 6, 2009 5:49 PM

Answer 1

Start with
URL url = getClass().getClassLoader().getResource(fileName)Then observe that URL has a [openStream()|http://java.sun.com/javase/6/docs/api/java/net/URL.html#openStream()] method that will give you an InputStream. Since you are reading text you might want to create an InputStreamReader from which you can do your reading much like you used the FileReader before when you were working with a File.
Class also has a [getResourceAsStream()|http://java.sun.com/javase/6/docs/api/java/lang/Class.html#getResourceAsStream(java.lang.String)] which combines the first two steps into one. Ie use getResource() as you mentioned when you want to get a URL that some other class will use to read (eg an image) or use getResourceAsStream() when you are going to do the reading yourself.