Java abstract class and abstract method

Example5_12.java

Abstract classA {Abstract intAddintXinty); intSubintXinty) {returnX-y; }}classBextendsA {intAddintXintY) {//subclasses must override the parent class's Add method      returnx+y; }} Public classExample5_12 { Public Static voidMain (String args[]) {b b=NewB (); intSum=b.add (30,20);//call the subclass override of the Add method      intSub=b.sub (30,20);//Call sub method inherited by subclassSystem.out.println ("sum=" +sum);//output is sum=50System.out.println ("sum=" +sub);//output is sum=10A;//abstract class declaration ObjectA = b;//A is the upper transition object of BSum=a.add (30,20);//calling a subclass override methodSub=a.sub (30,20);//methods that call subclass inheritanceSystem.out.println ("sum=" +sum);//output is sum=50System.out.println ("sum=" +sub);//output is sum=10   }}

Java abstract class and abstract method