In this example we shall show you how to override a super class field in a subclass. To override a super class field in a subclass we have performed the following steps:
- We have created a class,
Athat has a final int field set to 1, and an int field. It has anint getAttr()that prints a message and returns the int field. - Class
BextendsAand also has a final int field set to 2. It also has a methodint getAttr()that calls its superclassgetAttr()and returns its int field. - We create a new instance of
Aand call itsgetAttr()method. - We also create a new instance of
Bclass and call itsgetAttr()method. - Then we create a new
Aobject, usingBconstructor and use the object’sgetAttr()method. - In order that B object is initialized A constructor is first called,
as described in the code snippet below.
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 | package com.javacodegeeks.snippets.core;class A { final int field = 1; int x; int getAttr() { System.out.println("In OA.getAttr"); return field; }}class B extends A { final int field = 2; int getAttr() { System.out.println("In OB.getAttr"); super.getAttr(); // Just to show flow of control return field; }}public class OverridingFields { public static void main(String[] av) { System.out.println("A's getAttr returns: " + new A().getAttr()); System.out.println("B's getAttr returns: " + new B().getAttr()); // Declared as A, instantiated as B, so gets B's version of things. A c = new B(); System.out.println("C's version of getAttr returns: " + c.getAttr()); }} |
Output:
In A.getAttr
A's getAttr returns: 1
In B.getAttr
In A.getAttr
B's getAttr returns: 2
In B.getAttr
In A.getAttr
C's version of getAttr returns: 2
This was an example of how to override a super class field in a subclass in Java.
