Loading resources (images) contained in a .Jar file or in the classpath

Question

So I\'ve tried various reading various fixes for this problem on stack exchange most say to use getResourceAsStream() method, which I have done. This is my Reso

Answer 1

The question of how to load classpath resources is quite recurring, and a bit confusing for a Java newbie: some answers suggest class.getClassLoader().getResourceAsStream, others class.getResourceAsStream, although they have a slight different semantic:

1. class.getResourceAsStream does a path translation
2. class.getClassLoader().getResourceAsStream does not translate the path

For better show the difference, I'm going to propose the following test class, which in 4 different ways try to load the same resource (an image), only 2 working depending on the used path. The Jar content-tree is:

The class:

package image;

import java.io.InputStream;

public class ImageLoader {
    public static void main(String[] args ){
        String cmd = null;
        InputStream is = null;
        final String image = "save.png";

        if("test1".equals(args[0])){
            cmd = "ImageLoader.class.getClassLoader().getResourceAsStream(\""+image+"\")";
            is = ImageLoader.class.getClassLoader().getResourceAsStream(image);     //YES, FOUND


        }else if("test2".equals(args[0])){
            cmd = "ImageLoader.class.getResourceAsStream(\""+image+"\")";
            is = ImageLoader.class.getResourceAsStream(image);                      //NOT FOUND

        }else if("test3".equals(args[0])){
            cmd = "ImageLoader.class.getResourceAsStream(\"/"+image+"\")";
            is = ImageLoader.class.getResourceAsStream("/"+image);                  //YES, FOUND

        }else if("test4".equals(args[0])){
            cmd = "ImageLoader.class.getClassLoader().getResourceAsStream(\"/"+image+"\")";
            is = ImageLoader.class.getClassLoader().getResourceAsStream("/"+image); //NOT FOUND

        }else {
            cmd = " ? ";
        }

        System.out.println("With "+cmd+", stream loaded: "+(is != null));
    }
}

Run with:

java -cp resLoader.jar image.ImageLoader test4

Hope this class can help in understanding the different behaviour.