Java: Extending Class At Runtime

Question

I have the capability to extend a class at compile time, but I need to be able to create an instance of this subclass at runtime using an instance of the superclass that was

Answer 1

I don't know if it's a sollution but if you have

public static Foo foo = new Foo();

and you want to replace it with Bar which extends Foo make Bar an Wrapper for of Foo and use reflection to let foo point to your Bar instance.

public class Foo extends Bar {
  private bar; 
  public Foo(Bar oldInstance) {
     this.bar = oldInstance;
  }
}

and

// exception handling ommitted
public static void onStartup() {
   Class fooRefClass = FooRef.class;
   Field fooRef = fooRefClass.getDeclaredField("foo");

   Foo foo = (Foo)fooRef.get(null);
   Bar bar = new Bar(foo);
   fooRef.set(null, bar);

}

As told I don't know if this is possible in your case.