Question

So the situation is something like this:

private void myMethod()
{
    System.out.println("Hello World"); //some code

    System.out.println("Some Other Stuff"); 

    System.out.println("Hello World"); //the same code. 

}

We don’t want to be repeating our code.

The technique described here works pretty well:

private void myMethod()
{
    final Runnable innerMethod = new Runnable()
    {
        public void run()
        {
            System.out.println("Hello World"); 
        }
    };

    innerMethod.run();
    System.out.println("Some other stuff"); 
    innerMethod.run(); 
}

But what if I want to pass in a parameter to that inner method?

eg.

private void myMethod()
{
    final Runnable innerMethod = new Runnable()
    {

        public void run(int value)
        {
            System.out.println("Hello World" + Integer.toString(value)); 
        }
    };

    innerMethod.run(1);
    System.out.println("Some other stuff"); 
    innerMethod.run(2); 
}

gives me: The type new Runnable(){} must implement the inherited abstract method Runnable.run()

While

private void myMethod()
{
    final Runnable innerMethod = new Runnable()
    {
        public void run()
        {
            //do nothing
        }

        public void run(int value)
        {
            System.out.println("Hello World" + Integer.toString(value)); 
        }
    };

    innerMethod.run(1);
    System.out.println("Some other stuff"); 
    innerMethod.run(2); 
}

gives me The method run() in the type Runnable is not applicable for the arguments (int).

Answer 1

Looks like you just want inner methods. Java does’t let you have them, so the Runnable hack you describe lets you sort-of declare an inner method.

But since you want more control over it, why not define your own:

interface Inner<A, B> {
    public B apply(A a);
}

Then you can say:

private void myMethod(..){ 
    final Inner<Integer, Integer> inner = new Inner<Integer, Integer>() {
        public Integer apply(Integer i) {
            // whatever you want
        }
    };


    // then go:
    inner.apply(1);
    inner.apply(2);

}

Or use some library that provides functor objects. There should be many. Apache Commons has a Functor that you can use.