class or interface ?

import java.lang.*;

interface RR { void mR(); }
abstract class CC_Base
{
  protected RR r;
  public abstract void t(int i);
}

class CC01 extends CC_Base
{
  protected class CC01_inner implements RR
  {
    public CC01_inner(){}
    public void mR(){ System.out.println("CC01_inner!!"); }
  }

  public CC01(){ r = new CC01_inner(); }
  public void m( int i ){ r.mR(); }
  public void t( int i ){ System.out.println("CC01 " + i); }
}

class CC02 extends CC_Base
{
  protected class CC02_inner implements RR
  {
    public CC02_inner(){}
    public void mR(){ System.out.println("CC02_inner!!"); }
  }

  public CC02(){ r = new CC02_inner(); }
  public void m( String s ){ System.out.println(s); r.mR(); }
  public void t( int i )   { System.out.println("CC02 " + i); }
}

public class test02
{
  public static void main(String[] args){
    CC01 cc = new CC01();
    cc.m(32);
    cc.t(111);
    /*
      CC02 cc = new CC02();
      cc.m("Test");
      cc.t(333);
    */
  }
}