OOPs Concepts in Java

List of OOPs Concepts in Java

There are four main OOPs concepts in Java. These are:

• Abstraction. Abstraction means hiding internal details of the program and showing the only functionality of the program. for example, We all know how to turn the TV on, but we don’t need to know how it works internally in order to enjoy it.
• Encapsulation. This is the practice of keeping fields within a class private, then providing access to them via public methods. It’s a protective barrier that keeps the data and code safe within the class itself.
• Inheritance. This is a special feature of Object Oriented Programming in Java. It lets programmers create new classes that share some of the attributes of existing classes.
• Polymorphism. This Java OOPs concept lets programmers use the same word to mean different things in different contexts.

 

How Abstraction Works

Abstraction as an OOPs concept in Java works by letting programmers create useful, reusable tools. For example, a programmer can create several different types of objects. These can be variables, functions, or data structures. Programmers can also create different classes of objects. These are ways to define the objects.

For instance, a class of variable might be an address. The class might specify that each address object shall have a name, street, city, and zip code. The objects, in this case, might be employee addresses, customer addresses, or supplier addresses.

How Encapsulation Works

It’s a powerful OOPs concept in Java because it helps us save a lot of time.  Encapsulation lets us do that while keeping our original data private. It also lets us alter our original code without breaking it for others who have adopted it in the meantime.

How Inheritance Works

Inheritance is another labor-saving Java OOPs concept. It works by letting a new class adopt the properties of another. We call the inheriting class a subclass or a child class. The original class is often called the parent. We use the keyword extends to define a new class that inherits properties from an old class.

How Polymorphism Works

Polymorphism in Java works by using a reference to a parent class to affect an object in the child class. We might create a class called “horse” by extending the “animal” class. That class might also implement the “professional racing” class. The “horse” class is “polymorphic,” since it inherits attributes of both the “animal” and “professional racing” class.

Two more examples of polymorphism in Java are method overriding and method overloading.

In method overriding, the child class can use the OOP polymorphism concept to override a method of its parent class. That allows a programmer to use one method in different ways depending on whether it’s invoked by an object of the parent class or an object of the child class.

In method overloading, a single method may perform different functions depending on the context in which it’s called. That is, a single method name might work in different ways depending on what arguments are passed to it.

 

Short Encapsulation Example in Java

In the encapsulation is demonstrated as an OOPs concept in Java. Here, the variable “name” is kept private or “encapsulated.”

//save as Student.java
package com.javatpoint;
public class Student {
 private String name;
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name
 }
}
//save as Test.java
package com.javatpoint;
class Test {
 public static void main(String[] args) {
  Student s = new Student();
  s.setName(“vijay”);
  System.out.println(s.getName());
 }
}

Example of Inheritance in Java

It’s quite simple to achieve inheritance as an OOPs concept in Java. Inheritance can be as easy as using the extends keyword:

class Mammal {

}
class Aardvark extends Mammal {

}

Short Example of Polymorphism in Java

In the example below of polymorphism as an OOPs concept in Java, we have two classes: Person and Employee. The Employee class inherits from the Person class by using the keyword extends. Here, the child class overrides the parent class.

class Person {
 void walk() {
  System.out.println(“Can Run….”);
 }
}
class Employee extends Person {
 void walk() {
  System.out.println(“Running Fast…”);
 }
 public static void main(String arg[]) {
  Person p = new Employee(); //upcasting
  p.walk();
 }
}