Java Small Note (i)

The issues you need to be aware of in Java for up-transformation, down-conversion, and internal classes:

Upward transformation and downward transformation:

For example: There are 2 classes, Father is the parent class, and the son class inherits from father.

Father f1 = new Son (); This is called upcasting (upward transformation)

Now the F1 reference points to a son object

son S1 = (son) F1; This is called downcasting (downward transformation)

Now F1 still point to son object

But we cannot do this when we are going down the transition:

Father F2 = new Father ();

Son s2 = (son) F2; Error, subclass reference cannot point to parent class object

Inner class:

When you create an inner class, you must use an object from the outer class to create

Java Small Note (i)