Question

I created a jar file for my project , but the following warning appeared , and when double click on it , it does not open

warning: [options] bootstrap class path not set in conjunction with -source 1.6
1 warning

I’m using NetBeans 7.0.1 / Windows 7

Answer 1

The warning is not necessarily the problem with making it clickable.

To make a JAR executable, you have to specify the ‘main’ class in the JAR’s ‘manifest’ file, for example:

  Manifest-Version: 1.0
  Main-Class: MyMainClass

You then create the jarfile, specifying the manifest file above. If doing this manually, it’s something like:

jar cvfm myapp.jar myManifest *.class

If you created the JAR from NetBeans instead, I expect there’s a setting for this:

Updated see Producing executable jar in NetBeans for information on this.

If you don’t specify the main class, then the JAR can be used as a library, but it can’t be executed directly as a program without using a commandline script to specify which class to run, e.g.

java -cp myjar.jar com.myco.myproj.MyMainClass

which runs Java, putting your jarfile on the classpath (i.e. making all your classes available) and specifies that MyClass is the main class, i.e. the starting point for your application. MyClass must have a main method defined, or this won’t work.