java compiled classes contain dollar signs

Inner classes, if any present in your class, will be compiled and the class file will be ClassName$InnerClassName. In case of Anonymous inner classes, it will appear as numbers. Size of the Class (Java Code) doesn’t lead to generation of multiple classes.

E.g. given this piece of code:

public class TestInnerOuterClass {
    class TestInnerChild{

    }

    Serializable annoymousTest = new Serializable() {
    };
}

Classes which will be generated will be:

1. TestInnerOuterClass.class
2. TestInnerOuterClass$TestInnerChild.class
3. TestInnerOuterCasss$1.class

Update:

Using anonymous class is not considered a bad practice ,it just depends on the usage.

Check this discussion on SO