testoverload.java

北京大学出版社的

package examples.inheritance;

class SuperOverload { 
    public String toString() {
       return "superclass";
    }
}

class SubOverload extends SuperOverload {
   public String toString() {
      return "subclass";
   }
}

public class TestOverload {
   public static void main( String[] args ) {
      SuperOverload a = new SuperOverload();
      SubOverload b = new SubOverload();

      // SubOverload.toString
      System.out.println( a.toString() );
      // SuperOverload.toString
      System.out.println( b.toString() );

      // a is a SuperOverload ref to SubOverload object
      a = b;

      // SubOverload.toString
      System.out.println( a.toString() );
   }
}