MyJarExplorer is a program that will let you view and edit Java .jar files.
If you have associated the .JAR extension with this program, it will open when you double click on any Java .jar file. It will run a .bat where it will start the program from a command prompt. This program is made in Java, so it runs under many operating systems. You should have Java version 1.6 or higher installed in the computer. If you are trying to run this program in a UNIX system, you should copy the "bin" directory and statup.sh file, and edit startup.sh to set the correct classpath.
When you open a .jar file using MyJarExplorer, the program interface will show two frames. You will see each one of the names of the components in the program (classes, text files, pngs, etc.) on the left, If you click on any of those names, the program will show you the content of the selected component on the right frame. There, you can edit the content as you like, search any desired string, and then save the edited content to a new file. You can also search for any class, and the program will show it to you.