Lecturer lec = (Lecturer)objRef; 
lec.age = 21;

is an example of Downcasting

Person objRef = new Lecturer(); 
objRef.name = "Goo";

is an example of Upcasting

objRef.display(); 
lec.display();

outputs:

The code will not compile.

System.out.println(lec.name + "/" + lec.age);

outputs:

Goo/21