为什么 getClass 返回类名 + $1（或 $*）

Question

I'm writing a piece of code in which I have to cast an Object if it is an instance of a certain class.

As usual I'm using instanceof for checking the compatibility.

The problem is that the check is never satisfied because the objects belong to "strange" classes.

For example; when I call the method getClass().getSimpleName() on this object it return me the name of the class + $* (eg ViewPart$1 instead of ViewPart ).

What does this $* means? Is there a solution or a workaround?

Answer 1

That shows an inner class (either anonymous (if it has a number) or named). For example:

class Foo {
    static class Bar {
    }
}

The name of class Foo.Bar is Foo$Bar . Now if we had:

class Foo {

    static void bar() {
        Runnable r = new Runnable() {
            public void run() {};
        };

        System.out.println(r.getClass());
    }
}

That will print Foo$1 .

You can see the same effect in the naming of the class files created by javac.

Answer 2

These are instances of an anonymous class . ViewPart$1 is the first anonymous class defined inside ViewPart - but that doesn't mean it's a subclass of ViewPart . It's most likely an anoymous implementation of some Listener interface.

Answer 3

$ denotes for inner class. For example consider two classes

public class TopClass {
  class SubClass {
     // some methods
  }// inner class end
} // outer class end

If you compile this code you will get two class files TopClass.class and TopClass$SubClass.class.

Check your ViewPart class whether it has any inner classes. Hope it helps.