Java Inheritance

Java Inheritance defines an is-a relationship between a super class and its sub classes.This means that an object of a subclass can be used wherever an object of the superclass can be used. Class Inheritance in java mechanism is used to build new classes from existing classes. The inheritance relationship is transitive: if class x extends class y, then a class z, which extends class x, will also inherit from class y.
For example a car class can inherit some properties from a general vehicle class. Here we find that the base class is the vehicle class and the subclass is the more specific car class. A subclass must use the extends clause to derive from a super class which must be written in the header of the subclass definition. The subclass inherits members of the super class and hence promotes code reuse. The subclass itself can add its own new behavior and properties. Object class is always at the top of any Class inheritance hierarchy.

class Box {

    double width;
    double height;
    double depth;
    Box() {
    }
    Box(double w, double h, double d) {
        width = w;
        height = h;
        depth = d;
    }
    void getVolume() {
        System.out.println("Volume is : " + width * height * depth);
    }
}

public class MatchBox extends Box {

    double weight;
    MatchBox() {
    }
    MatchBox(double w, double h, double d, double m) {
        super(w, h, d);
        weight = m;
    }
    public static void main(String args[]) {
        MatchBox mb1 = new MatchBox(10, 10, 10, 10);
        mb1.getVolume();
        System.out.println("width of MatchBox 1 is " + mb1.width);
        System.out.println("height of MatchBox 1 is " + mb1.height);
        System.out.println("depth of MatchBox 1 is " + mb1.depth);
        System.out.println("weight of MatchBox 1 is " + mb1.weight);
    }
}

Output

Volume is : 1000.0
width of MatchBox 1 is 10.0
height of MatchBox 1 is 10.0
depth of MatchBox 1 is 10.0
weight of MatchBox 1 is 10.0

Posted in: Inheritance in Java