Runtime polymorphism example

PolymorphismExample.java

package polymorphism.runTime;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

//https://gist.github.com/rajeevprasanna/8500647
public class PolymorphismExample {
	public static void main(String[] args) {
		List workers = new ArrayList();

		// Adding worker one
		Worker worker1 = new Principal();
		workers.add(worker1);

		// Adding worker two
		Worker worker2 = new Teacher();
		workers.add(worker2);

		for (Iterator iterator = workers.iterator(); iterator.hasNext();) {
			Worker worker = (Worker) iterator.next();
			worker.doIt();
		}
		// op : Principal does the work
		// Teacher does the work

		// If you see carefully, we cannot see which instance is called. We
		// called doIt() method only on the Super type Worker but the JVM finds
		// the proper type and called its implementation of doIt() method. This
		// is Runtime Polymorphism. The JVM determines proper type only at
		// runtime
	}
}

Principal.java

package polymorphism.runTime;

public class Principal implements Worker {
	public void doIt() {
		System.out.println("Principal does the work");
	}
}

Teacher.java

package polymorphism.runTime;

public class Teacher implements Worker {
	public void doIt() {
		System.out.println("Teacher does the work");
	}
}

Worker.java

package polymorphism.runTime;

public interface Worker {
	public void doIt();
}