Upcasting in java

Upcasting

• Once you have upcast an object reference, you can access only the fields and methods declared by the base class.
  • For example, if Manager is a subclass of Employee:

    Employee e = new Manager(...);

  • Now using e you can access only the fields and methods declared by the Employee class.
• However, if you invoke a method on e that is defined in Employee but overridden in Manager, the Manager version is executed.
  • For example:

    public class A {
        public void print() {
            System.out.println("Hello from class A");
        }
    }
    public class B extends A {
        public void print() {
            System.out.println("Hello from class B");
        }
    }
    // ...
    A obj = new B();
    obj.print();

    In the case, the output is "Hello from class B".

From within a subclass, you can explicitly invoke a base class’s version of a method by using the super. prefix on the method call.