• Skip to main content
  • Skip to primary sidebar
  • Skip to secondary sidebar
  • Skip to footer

Computer Notes

Library
    • Computer Fundamental
    • Computer Memory
    • DBMS Tutorial
    • Operating System
    • Computer Networking
    • C Programming
    • C++ Programming
    • Java Programming
    • C# Programming
    • SQL Tutorial
    • Management Tutorial
    • Computer Graphics
    • Compiler Design
    • Style Sheet
    • JavaScript Tutorial
    • Html Tutorial
    • Wordpress Tutorial
    • Python Tutorial
    • PHP Tutorial
    • JSP Tutorial
    • AngularJS Tutorial
    • Data Structures
    • E Commerce Tutorial
    • Visual Basic
    • Structs2 Tutorial
    • Digital Electronics
    • Internet Terms
    • Servlet Tutorial
    • Software Engineering
    • Interviews Questions
    • Basic Terms
    • Troubleshooting
Menu

Header Right

Home » Java » Classes » Overriding Constructors in Java
Next →
← Prev

Overriding Constructors in Java

By Dinesh Thakur

Super-class constructors cannot be overridden as the constructors have the same name as their class. To be able to access a constructor in a sub-class with the same number and data type of arguments as in the super-class, it must be defined in the sub-class itself. When constructors are defined in a sub-class, the corresponding super-class constructors are called during the creation of objects of that sub-class. This ensures that the initialization of inherited parts of the objects takes place similar to the way the super-class initializes its objects. Thus, defining constructors explicitly in the sub-class will override or overload super-class constructors.

Generally, super-class methods are called using the following syntax:

super.methodname( arguments-list)

This syntax cannot be used in the case of constructors, as constructors do not have a method name. The constructors of the super-class are called without having method name as shown below:

super( arguments-list)

Java follows specific rules for the use of keyword super()

1. The first calling method must be super() in the constructor’s definition. If the super() method is not specified, Java will implicitly call the super() method with no arguments.

2. Super() is used to call a constructor method with the appropriate arguments from the immediate super-class. This may, in turn, call the constructor of its super-class and so on. The usage of super() in the constructor is similar to the use of keyword this().

3. To use super() in the constructor of sub-class, a constructor with the same signature must exist in the super-class.

A constructor in the super-class with exactly the same signature as the constructor in the sub-class need not be called from the sub-class. Only those constructors for which values need to be initialized in the sub-class should be called. The programmer can therefore simply create sub-classes that have constructors with entirely different signatures from any of the super-class constructors. Program illustrates how this can be done.

Using constructors with different signatures in the sub-class and super-class.

import java.io.*;
class One {
  int num;
  One(int n) {
    this.num = n;
  }
 void show() {
    System.out.println ("num" +num);
 }
}
class Two extends one {
  int num1;
  Two(int x, int y) {
    super(x);
    num1 = y;
  }
 void show() {
   System.out.println("sub class number"+num1);
   System.out.println("super class number"+num);
   super.show();
 }
}
class SampleClass {
 public static void main(String args[ ]) {
   Two t = new Two(100,200);
   t.show();
 }
}

The output of SampleClass program is as shown below:

sub class number 200

super class number 100

num 100

Program defines a class SimpleClass. It creates an object of class Two which extends the class One. The class One has only one constructor, which assigns the value of n to num. The class Two has an additional instance variable (y in this example) and defines a constructor to initialize x and y. The constructor defined in the program calls the constructor method belonging to class One to initialize the instance variable x of class Two.

You’ll also like:

  1. Overriding in Java
  2. Method Overriding in Java with Examples
  3. What is Constructors? Type of Constructors.
  4. String Constructors in Java with Example
  5. Constructors and Methods of the Thread Class in Java with Example
Next →
← Prev
Like/Subscribe us for latest updates     

About Dinesh Thakur
Dinesh ThakurDinesh Thakur holds an B.C.A, MCDBA, MCSD certifications. Dinesh authors the hugely popular Computer Notes blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps.

Dinesh Thakur is a Freelance Writer who helps different clients from all over the globe. Dinesh has written over 500+ blogs, 30+ eBooks, and 10000+ Posts for all types of clients.


For any type of query or something that you think is missing, please feel free to Contact us.


Primary Sidebar

Java Tutorials

Java Tutorials

  • Java - Home
  • Java - IDE
  • Java - Features
  • Java - History
  • Java - this Keyword
  • Java - Tokens
  • Java - Jump Statements
  • Java - Control Statements
  • Java - Literals
  • Java - Data Types
  • Java - Type Casting
  • Java - Constant
  • Java - Differences
  • Java - Keyword
  • Java - Static Keyword
  • Java - Variable Scope
  • Java - Identifiers
  • Java - Nested For Loop
  • Java - Vector
  • Java - Type Conversion Vs Casting
  • Java - Access Protection
  • Java - Implicit Type Conversion
  • Java - Type Casting
  • Java - Call by Value Vs Reference
  • Java - Collections
  • Java - Garbage Collection
  • Java - Scanner Class
  • Java - this Keyword
  • Java - Final Keyword
  • Java - Access Modifiers
  • Java - Design Patterns in Java

OOPS Concepts

  • Java - OOPS Concepts
  • Java - Characteristics of OOP
  • Java - OOPS Benefits
  • Java - Procedural Vs OOP's
  • Java - Polymorphism
  • Java - Encapsulation
  • Java - Multithreading
  • Java - Serialization

Java Operator & Types

  • Java - Operator
  • Java - Logical Operators
  • Java - Conditional Operator
  • Java - Assignment Operator
  • Java - Shift Operators
  • Java - Bitwise Complement Operator

Java Constructor & Types

  • Java - Constructor
  • Java - Copy Constructor
  • Java - String Constructors
  • Java - Parameterized Constructor

Java Array

  • Java - Array
  • Java - Accessing Array Elements
  • Java - ArrayList
  • Java - Passing Arrays to Methods
  • Java - Wrapper Class
  • Java - Singleton Class
  • Java - Access Specifiers
  • Java - Substring

Java Inheritance & Interfaces

  • Java - Inheritance
  • Java - Multilevel Inheritance
  • Java - Single Inheritance
  • Java - Abstract Class
  • Java - Abstraction
  • Java - Interfaces
  • Java - Extending Interfaces
  • Java - Method Overriding
  • Java - Method Overloading
  • Java - Super Keyword
  • Java - Multiple Inheritance

Exception Handling Tutorials

  • Java - Exception Handling
  • Java - Exception-Handling Advantages
  • Java - Final, Finally and Finalize

Data Structures

  • Java - Data Structures
  • Java - Bubble Sort

Advance Java

  • Java - Applet Life Cycle
  • Java - Applet Explaination
  • Java - Thread Model
  • Java - RMI Architecture
  • Java - Applet
  • Java - Swing Features
  • Java - Choice and list Control
  • Java - JFrame with Multiple JPanels
  • Java - Java Adapter Classes
  • Java - AWT Vs Swing
  • Java - Checkbox
  • Java - Byte Stream Classes
  • Java - Character Stream Classes
  • Java - Change Color of Applet
  • Java - Passing Parameters
  • Java - Html Applet Tag
  • Java - JComboBox
  • Java - CardLayout
  • Java - Keyboard Events
  • Java - Applet Run From CLI
  • Java - Applet Update Method
  • Java - Applet Display Methods
  • Java - Event Handling
  • Java - Scrollbar
  • Java - JFrame ContentPane Layout
  • Java - Class Rectangle
  • Java - Event Handling Model

Java programs

  • Java - Armstrong Number
  • Java - Program Structure
  • Java - Java Programs Types
  • Java - Font Class
  • Java - repaint()
  • Java - Thread Priority
  • Java - 1D Array
  • Java - 3x3 Matrix
  • Java - drawline()
  • Java - Prime Number Program
  • Java - Copy Data
  • Java - Calculate Area of Rectangle
  • Java - Strong Number Program
  • Java - Swap Elements of an Array
  • Java - Parameterized Constructor
  • Java - ActionListener
  • Java - Print Number
  • Java - Find Average Program
  • Java - Simple and Compound Interest
  • Java - Area of Rectangle
  • Java - Default Constructor Program
  • Java - Single Inheritance Program
  • Java - Array of Objects
  • Java - Passing 2D Array
  • Java - Compute the Bill
  • Java - BufferedReader Example
  • Java - Sum of First N Number
  • Java - Check Number
  • Java - Sum of Two 3x3 Matrices
  • Java - Calculate Circumference
  • Java - Perfect Number Program
  • Java - Factorial Program
  • Java - Reverse a String

Other Links

  • Java - PDF Version

Footer

Basic Course

  • Computer Fundamental
  • Computer Networking
  • Operating System
  • Database System
  • Computer Graphics
  • Management System
  • Software Engineering
  • Digital Electronics
  • Electronic Commerce
  • Compiler Design
  • Troubleshooting

Programming

  • Java Programming
  • Structured Query (SQL)
  • C Programming
  • C++ Programming
  • Visual Basic
  • Data Structures
  • Struts 2
  • Java Servlet
  • C# Programming
  • Basic Terms
  • Interviews

World Wide Web

  • Internet
  • Java Script
  • HTML Language
  • Cascading Style Sheet
  • Java Server Pages
  • Wordpress
  • PHP
  • Python Tutorial
  • AngularJS
  • Troubleshooting

 About Us |  Contact Us |  FAQ

Dinesh Thakur is a Technology Columinist and founder of Computer Notes.

Copyright © 2023. All Rights Reserved.