A reference to an object can be cast into a reference to an object of its parent class. : Reference Type Casting « Type Casting « SCJP

1. SCJP
2. Type Casting
3. Reference Type Casting

public class MainClass{
    public static void main(String[] argv){
        MyClass myClass = new MyClass();
        MySubclass mySub = new MySubclass();
        myClass = mySub;
        System.out.println();
    }
}
    
class MyClass{
}
class MySubclass extends MyClass{

}