Using Parent reference to store child class objects

poly.java

class Alpha
{
	String getType() 
	{ 
		return "alpha"; 
	}
}

class Beta extends Alpha
{
	String getType() 
	{ 
		return "beta"; 
	}
}

class Gamma extends Beta 
{
	String getType() 
	{ 
		return "gamma"; 
	}
}
public class Poly
{
	public static void main(String[] args) 
	{
		Alpha a1 = new Alpha();
		Alpha a2 = new Beta();
		Alpha a3 = new Gamma();
		System.out.println(a1.getType());
		System.out.println(a2.getType());
		System.out.println(a3.getType());
	}
}