Calling a method of subclass through reflection

Question

Here is my superclass Animal

class Animal
{
   //Empty
}

My subclass Tiger

class Tiger extends Animal
{
    public static void TigerPrint()
    {     -------
        System.out.println("Tiger");
    }
    public void Run()
    {
         System.out.println("Tiger Running");
    }
}

Now I do,

  Animal a=new Tiger();

At compile time a would be an Animal.At runtime it would be Tiger.

So,I did

a.getClass().getMethod("TigerPrint").invoke(null);//WORKS
a.getClass().getMethod("Run").invoke(null);//NOT WORKING (NullPointerException)

How can I call the Run method of subclass through reflection.

Yes I can do

((Tiger)a).Run();

But how can i do that in reflection!

score 7 · Accepted Answer · answered Feb 10 '13 at 18:36

7

You are invoking an instance method on a null instance - so it makes sense that you receive a NPE. Try this instead (passing an instance to the invoke method instead of null):

a.getClass().getMethod("Run").invoke(a);

Note: the first call worked because you can call a static method on a null instance without causing a NPE.

answered Feb 10 '13 at 18:36

assylias

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@Arpit You can comment here if you want - not sure how the chat works on SO to be honest. – assylias Feb 10 '13 at 18:39

score 0 · Answer 2 · answered Feb 10 '13 at 18:41

0

you have two choices either make run() method static and remain with current call or change the current call to pass the object instance as assylias pointed.

answered Feb 10 '13 at 18:41

Arpit

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Calling a method of subclass through reflection

2 Answers2

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