Reduce visibility when implementing interface in Java

Question

I would like to design class A implements interface C and reduce the visibility of a method (declared in C)to make it secure from outer world, make one of the methods in in

Answer 1

This approach worked for me. Any new function added to PrivateInterface would break still break PublicSampleClass

private interface PrivateInterface {
    void fooBar();
}

public class PublicSampleClass {

    private final listenerInterface = new PrivateInterface {
         public void fooBar() {
            PublicSampleClass.this.fooBar();
         }
    };

    protected void fooBar() {
      // Non public implementation
    }

}