Can I instantiate an anonymous class in the constructor of outer class?

Question

I have the following code:

public class Outer {
     public Interface Anony {
         public void callback();
     }

     public Outer() {
        OtherClass.foo(new Anony() {
            @Override
            public void callback() {
                ....
            }
        });
    }
}

But my friend told me that there is some issue in it. I created an anonymous class instance in the constructor of Outer, so the anonymous class instance implicitly references the Outer class instance, i.e. Outer.this. But at this moment, Outer class instance has not been fully created yet. So the anonymous class instance references an object with incomplete states, hence the issue.

Is he right? Thanks.

Answer 1

You friend is right, but it depends on the usage of course.

The problem is not in creating the inner class inside the constructor. The problem will occur IF the inner class accesses the outer class.

This is because any object will not be able to give normal grantees inside a constructor. All of the variables needed for the objects operations may not have been initialized, etc.

However if the inner class is put at the end of the constructor I don't see this problem occurring, but keep in mind this is a dangerous gambit because someone may modify the code and then it's wtf time with the debugger...