Inheritance in Java
Inheritance in Java
- Inheritance is an important pillar of OOP(Object Oriented Programming).
- It is the mechanism in java by which one class is allow to inherit the features(fields and methods) of another class.
- Super Class: The class whose features are inherited is known as super class(or a base class or a parent class).
- Sub Class: The class that inherits the other class is known as sub class(or a derived class, extended class, or child class). The subclass can add its own fields and methods in addition to the superclass fields and methods.
- Reusability: Inheritance supports the concept of “reusability”, i.e. when we want to create a new class and there is already a class that includes some of the code that we want, we can derive our new class from the existing class. By doing this, we are reusing the fields and methods of the existing class
The keyword used for inheritance is extends.
Syntax :
class derived-class extends base-class
{
//methods and fields
}
Example :-
class Employee
{
float salary=40000;
}
class Programmer extends Employee
{
int bonus=10000;
public static void main(String args[])
{
Programmer p=new Programmer();
System.out.println("Programmer salary is:"+p.salary);
System.out.println("Bonus of Programmer is:"+p.bonus);
}
} output:-Programmer salary is:40000.0
Bonus of programmer is:10000
Types of inheritance in java:-
On the basis of class, there can be three types of inheritance in java:1.single
2.multilevel
3.hierarchical.
void eat()
}
class Dog extends Animal
}
class TestInheritance
public static void main(String args[])
Dog d=new Dog();
d.bark();
d.eat();
}
2.Multilevel :-
void eat()
}
class Dog extends Animal{
void bark()
}
class BabyDog extends Dog
void weep()
}
class TestInheritance2
public static void main(String args[])
BabyDog d=new BabyDog();
d.weep();
d.bark();
d.eat();
}
void eat()
}
class Dog extends Animal{
void bark()
}
class Cat extends Animal
void meow()
}
class TestInheritance3
public static void main(String args[])
Cat c=new Cat();
c.meow();
c.eat();
}
Multiple Inheritance
Multiple Inheritance A class's capacity to inherit traits from several classes is referred to as multiple inheritances. This notion may be quite helpful when a class needs features from many sources.
Multiple inheritances, however, can result in issues like the diamond problem, which occurs when two superclasses share the same method or field and causes conflicts. Java uses interfaces to implement multiple inheritances in order to prevent these conflicts.
import java.io.*;
interface Vehicle {
// Abstract methods defined
void changeGear(int a);
void speedUp(int a);
void applyBrakes(int a);
}
// Class implementing vehicle interface
class Bicycle implements Vehicle{
int speed;
int gear;
// Change gear
@Override
public void changeGear(int newGear){
gear = newGear;
}
// Increase speed
@Override
public void speedUp(int increment){
speed = speed + increment;
}
// Decrease speed
@Override
public void applyBrakes(int decrement){
speed = speed - decrement;
}
public void printStates() {
System.out.println("speed: " + speed
+ " gear: " + gear);
}
}
// Class implementing vehicle interface
class Bike implements Vehicle {
int speed;
int gear;
// Change gear
@Override
public void changeGear(int newGear){
gear = newGear;
}
// Increase speed
@Override
public void speedUp(int increment){
speed = speed + increment;
}
// Decrease speed
@Override
public void applyBrakes(int decrement){
speed = speed - decrement;
}
public void printStates() {
System.out.println("speed: " + speed
+ " gear: " + gear);
}
}
class Main
{
public static void main (String[] args)
{
// Instance of Bicycle(Object)
Bicycle bicycle = new Bicycle();
bicycle.changeGear(2);
bicycle.speedUp(3);
bicycle.applyBrakes(1);
System.out.print("Bicycle present state : ");
bicycle.printStates();
// Instance of Bike (Object)
Bike bike = new Bike();
bike.changeGear(1);
bike.speedUp(4);
bike.applyBrakes(3);
System.out.print("Bike present state : ");
bike.printStates();
}
}
Multiple Inheritance in Java Using Interface
Java does not support multiple inheritance with classes to avoid ambiguity, but it supports multiple inheritance using interfaces.
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