java - How to override the behavior of a class if I have only its object? -

the question may stupid 1 ask but, kindly me on this. need override behavior of class, object of it. following code sample.

i want use method util.newchildcomponent(string id) in places.

class parentcomponent{     public parentcomponent(string id){}     protected void somebehavior(){} }  class childcomponent extends parentcomponent{     public childcomponent(string id){         super(id);     }     protected void childsbehavior(){} }  public class util {     public static parentcomponent newchildcomponent(string id)     {         parentcomponent fc = new childcomponent(id);         // initialize object, , performs common configuration.         // performs different operations on generated child object.         // child class has many members apart childsbehavior().         return fc;     } }   // above classes belongs jar, cannot edit code. // need use util.newchildcomponent(string id) // need override behavior mentioned below. public void f1() {     // todo: how override childsbehavior() method using object      // have in pc? possible?     // util.newchildcomponent(id) method decorates childcomponent     // need use same object , override childsbehavior() method only.     parentcomponent pc = util.newchildcomponent("childid");      // need achieve result below     /*     parentcomponent pc = new childcomponent(id){             @override             protected void childsbehavior(){                 super.somebehavior();                 // stuff here.             }         }; */ } 

thanks in advance.

sounds looking dynamicobjectadaptorfactory.

here's use of excellent object.

static class parentcomponent {      protected void somebehavior() {         system.out.println("parentcomponent somebehavior");     } }  static class childcomponent extends parentcomponent {      private childcomponent(string id) {      }      protected void childsbehavior() {         system.out.println("childsbehavior");     } }  public static class util {      public static parentcomponent newchildcomponent(string id) {         parentcomponent fc = new childcomponent(id);         // initialize object, , performs common configuration.         return fc;     } }  interface parent {      void somebehavior();  }  // adaptor. public static class adapter implements parent {      final parentcomponent parent;      private adapter(parentcomponent pc) {         this.parent = pc;     }      // override parent behaviour.     public void somebehavior() {         system.out.println("adapter invoke somebehaviour()");         parent.somebehavior();         system.out.println("adapter finished somebehaviour()");     }  }  public void test() {     parentcomponent pc = util.newchildcomponent("childid");     parent adapted = dynamicobjectadapterfactory.adapt(pc, parent.class, new adapter(pc));     adapted.somebehavior(); } 

prints:

adapter invoke somebehaviour() somebehavior adapter finished somebehaviour()