What is reflection and why is it useful?

Question

What is reflection, and why is it useful?

I\'m particularly interested in Java, but I assume the principles are the same in any language.

Answer 1

Simple example for reflection. In a chess game, you do not know what will be moved by the user at run time. reflection can be used to call methods which are already implemented at run time:

public class Test {

    public void firstMoveChoice(){
        System.out.println("First Move");
    } 
    public void secondMOveChoice(){
        System.out.println("Second Move");
    }
    public void thirdMoveChoice(){
        System.out.println("Third Move");
    }

    public static void main(String[] args) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException { 
        Test test = new Test();
        Method[] method = test.getClass().getMethods();
        //firstMoveChoice
        method[0].invoke(test, null);
        //secondMoveChoice
        method[1].invoke(test, null);
        //thirdMoveChoice
        method[2].invoke(test, null);
    }

}