Java-オブジェクトタイプ変換とinstanceof関数

正直本当に回りくどいです...

/*
 * 
 *                     ，               
 *         ，        
 *                         。         ，       
 *                 ，                        ，
 *                      
 * 
 * */
class GrandS extends Father{
	
	public static void main(String[] args){
		// a1        ，a2         
		GrandF a1 = new Father();
		GrandF a2 = new GrandS();
		
		//       ，              ，                     ‘ ’ 
		Father b1 = (Father) a1; 
		Father b2 = (Father) a2;
		
//		GrandS c1 = (GrandS) a1;  //       turn Father to GrandS，            
		
		GrandS c2 = (GrandS) a2;
		
//		  instanceof                                 .
		if(b1 instanceof GrandF) System.out.println("b1 belongs GrandF");
		if(a1 instanceof Father) System.out.println("a1 belongs Father");
		if(a1 instanceof GrandS) System.out.println("a1 belongs GrandS");
		else System.out.println("a1 does not belong GrandS");
		if(a2 instanceof GrandS) System.out.println("a2 belongs GrandS");
		if(c2 instanceof GrandF) System.out.println("c2 belongs GrandF");

	}
}

class Father extends GrandF {
	
}

class GrandF {
	
}