Public vs Private inner classes in Java

Question

I was reading introduction to Java programming and it does not have a good explanation regarding this topic and it made me wonder why should someone use a private inner class in java instead of using a public one.

They both can be used only by the outer class.

think it as a member of the class. why do you set a member private? — stinepike, Dec 13 '13 at 17:14
[Nested Classes](http://docs.oracle.com/javase/tutorial/java/javaOO/nested.html) tutorial. — mre, Dec 13 '13 at 17:15
@StinePike to negate acess to another class.@arshajii I thought it had something more. — Lind, Dec 13 '13 at 17:19

amit · Accepted Answer · 2013-12-13T17:23:34.717

Your claim They both can be used only by the outer class. is wrong:

public class A {
    private class B {}
    public class C {}
    public C getC() { 
        return new C();
    }
    public B getB() {
        return new B();
    }

}
public class Tryout {
    public static void main(String[] args) {
        A a = new A();
        A.B b = a.getB(); //cannot compile
        A.C c = a.getC(); //compiles perfectly
    }
}

Note that you can actually have an instance of A.C in another class and refer to it as C (including all its public declaration), but not for A.B.

From this you can understand, you should use private/public modifier for inner classes the same way you use it generally.

Public vs Private inner classes in Java

1 Answers1