Inheritance in Java is a mechanism in which one object acquires all the properties and behaviors of a parent object. It is an important part of OOPs (Object Oriented programming system). Inheritance in Java. The class from which the subclass is derived is called a superclass (also a base class or a parent class). Every class has one and only one direct superclass (single inheritance). In the absence of any other explicit superclass, every class is implicitly a subclass of Object. I'm trying to make a simple calculator using scanner and inheritance too, after i insert two numbers and operator i found this Exception the Exception is: Exception in thread 'main' java.util.
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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.
Important terminology:
Multiple inheritance is not supported in JAVA. Inheritance is one of the important concept of object oriented programming. The simple definition says inheritance provides mechanism that allows a class to inherit properties of another class. Inheritance Concept: Inheritance means inherit the properties and behavior of existing object in a new object. So there are many advantages of using inheritance in Java: Reusability: Child class can use the data members and function defined in the parent class. Using the same code for parent and child class, reduce the line of code. Testing and debugging code will be easier. The syntax for Inheritance: The extends keyword is used to depict inheritance in Java.
How to use inheritance in Java
The keyword used for inheritance is extends.
Syntax :
Example: In below example of inheritance, class Bicycle is a base class, class MountainBike is a derived class which extends Bicycle class and class Test is a driver class to run program.
// concept of inheritance // base class { public int gear; public Bicycle( int gear, int speed) this .gear = gear; } // the Bicycle class has three methods { } public void speedUp( int increment) speed += increment; public String toString() return ( 'No of gears are ' +gear + 'speed of bicycle is ' +speed); } // derived class { // the MountainBike subclass adds one more field public MountainBike( int gear, int speed, { super (gear, speed); } // the MountainBike subclass adds one more method { } // overriding toString() method @Override { 'nseat height is ' +seatHeight); public class Test public static void main(String args[]) System.out.println(mb.toString()); } |
Output:
In above program, when an object of MountainBike class is created, a copy of the all methods and fields of the superclass acquire memory in this object. That is why, by using the object of the subclass we can also access the members of a superclass.
Please note that during inheritance only object of subclass is created, not the superclass. For more, refer Java Object Creation of Inherited Class.
Illustrative image of the program:
In practice, inheritance and polymorphism are used together in java to achieve fast performance and readability of code.
Types of Inheritance in Java
Below are the different types of inheritance which is supported by Java.
// concept of single inheritance import java.lang.*; { { } { { } // Driver class { { g.print_geek(); g.print_geek(); } |
Output:
// concept of Multilevel inheritance import java.lang.*; { { } { { } { { } public class Main public static void main(String[] args) three g = new three(); g.print_for(); } |
Output:
// concept of Hierarchical inheritance import java.lang.*; { { } { { } { } // Drived class { { g.print_geek(); t.print_for(); } |
Output:
// concept of Multiple inheritance import java.lang.*; { } interface two public void print_for(); { } { public void print_geek() { } public void print_for() System.out.println( 'for' ); } // Drived class { { c.print_geek(); c.print_geek(); } |
Output:
Important facts about inheritance in Java
What all can be done in a Subclass?
In sub-classes we can inherit members as is, replace them, hide them, or supplement them with new members:
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