Compile time polymorphism example

PolymorphismExample.java

package polymorphism.compileTime;

public class PolymorphismExample {

	public void doSomething(Worker worker) {
		System.out.println("I'm a worker");
	}

	public void doSomething(Teacher teacher) {
		System.out.println("I'm a Teacher");
	}

	public void doSomething(Principal principal) {
		System.out.println("I'm a Principal");
	}

	public static void main(String[] args) {

		PolymorphismExample example = new PolymorphismExample();
		Worker principal = new Principal();
		Worker teacher = new Teacher();

		example.doSomething(principal);
		example.doSomething(teacher);
		/*
		 * You would expect the output as bellow, If you run the
		 * PolymorphismExample class
		 * 
		 * I'm a Principal I'm a Teacher
		 * 
		 * WRONG, the actual output will be
		 * 
		 * I'm a worker I'm a worker
		 * 
		 * Here the type is decided at compile time. Even though the objects are
		 * instances of Principal and Teacher, the reference is a Worker type.
		 * So the compiler picks the doSomething(Worker worker) method as it
		 * accepts the same type of reference type
		 */
	}
}

Principal.java

package polymorphism.compileTime;

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

Teacher.java

package polymorphism.compileTime;

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

Worker.java

package polymorphism.compileTime;

public interface Worker {
	public void doIt();
}