Java Inheritance | Java example

Java Inheritance :

Inheritance is acquiring the properties of parent class in child class. Re-usability is the important aspect of programming.

By extending a class you can use the properties and also add new methods in child class.

There are 3 types of java inheritance

1. Single Inheritance
2. Multi-level Inheritance
3. Hierarchical Inheritance

Single Inheritance:

In single inheritance there is a  parent/base class and child/derived class.

Create a parent class with a add method accepting two variables.

class Parent {

    void add(int x, int y) {

        System.out.println("Result of addition is " + (x + y));
    }

}

And acquire the add method and can also add additional methods into derived class as

class SingleInheritance extends Parent {

    public static void main(String args[]) {

        SingleInheritance singleInheritance = new SingleInheritance();
        singleInheritance.add(1, 2);
        singleInheritance.sub(2, 1);

    }

    void sub(int x, int y) {

        System.out.println("Result of substraction is " + (x - y));
    }
}

Multi Level Inheritance:

In multilevel inheritance three are more than one derived class i.e., a derived class is further derived.

class Parent {

    void add(int x, int y) {

        System.out.println("Result of addition is " + (x + y));
    }

}

from which a intermediate class acquires properties

class Intermediate extends Parent {

    void sub(int x, int y) {

        System.out.println("Result of substraction is " + (x - y));
    }

}

now we can again acquire the properties of intermediate class

class MultilevelInheritance extends Intermediate {

    public static void main(String args[]) {

        MultilevelInheritance multilevelInheritance = new MultilevelInheritance();
        multilevelInheritance.add(1, 2);
        multilevelInheritance.sub(2, 1);
        multilevelInheritance.multiply(2, 3);

    }

    void multiply(int x, int y) {

        System.out.println("Result of multiplication is " + (x * y));
    }
}

Hierarchical Inheritance:

In hierarchical inheritance we can derive more classes from a single base class.

Create a base class

class ID {

    String id() {

        return "";
    }

}

inherit in from multiple classes as follow

Consider a student class having id

class Student extends ID {

    String id() {

        return "Student 01";
    }

}

Employee class with id

class Employee extends ID {

    String id() {

        return "Employee 01";
    }

}

now we can check how this inheritance works in real time

class HierarchialInheritance {

    public static void main(String args[]) {

        ID i = new Student();
        System.out.println(i.id());

        i = new Employee();
        System.out.println(i.id());

    }

}

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