Question

While compiling the code of Tic Tac Toe and also while running some codes in java using swing and awt packages. I’m getting a $ appended class file generation, parallel to the ClassName.class file. What may be the reason? Its Whether due to the usage of ActionListeners, it Happens. Usually these kind of creation of .bak file will be generated while doing C programs involving structures.

Support needed regarding these two scenarios.

Answer 1

Class files containing $ in their names are nothing but the inner classes or anonymous inner classes that you might have used inside your top-level class.

For e.g, If you have a class declaration like this: –

public class A {
    public class B {
    }
}

Then you will have two class files generated: – A.class and A$B.class.
This shows the containment of class B inside class A.

In case of ActionListener this is what is happening, in your code.

UPDATE: –

If you are using anonymous inner class, then also you will get class name with $ in it: –

interface A {
   public void show();
}

public class Foo {
    public static void main(String[] a) {

        new A() {
            @Override
            public void show() {
                System.out.println("Hello");
            }
        }.show();
    }
}

Then the class files generated will be: – Foo.class and Foo$1.class.

So, if you are using ActionListener as anonymous inner class, then also you would get that $, in your class file name for that anonymous inner class.