Question

In Java, how can I have a Runnable class that, depending on its constructor, selects its function?

For example:

Class A implements Runnable {

    public A(int var) {
        //things go here
    }

    public A(int var1, String var2) {
        //things go here
    }

    public void run() {
        //do (a) if Constructor A(int var)
        //do (b) if Constructor A(int var1, String var2)
    }
}

Answer 1

I would setup a Strategy Pattern:

class A implements Runnable {

    private final ExecutionStrategy strategy;

    public A(int var) {   
        strategy = new FooStrategy();
    }

    public A(int var1, String var2) {
        strategy = new BarStrategy();
    }

    public void run() {
        strategy.exec();
    }

    interface ExecutionStrategy { 
        public void exec();
    }

    private class FooStrategy implements ExecutionStrategy { 
        @Override
        public void exec() { 
        //implement me
        }
    }

    private class BarStrategy implements ExecutionStrategy { 
        @Override
        public void exec() { 
        //implement me
        }
    }
}