Encapsulation in Java with Examples

Encapsulation

Introduction

Encapsulation is an OOPS concept. It is a process of wrapping the data (variables) and code together into a single unit.

It is a concept of hiding data in a class, from other classes using data hiding. That’s why it is also known as data hiding.

What is Encapsulation?

It is wrapping code(method) and data (variables) together into one single unit.

A real-life example of Encapsulation, is A Capsule, in that capsule several medicines are mixed, and it is wrapped into one outer layer.

In the above diagram, you can see a class have data member and method (behavior) and both are combining. It makes that class an encapsulation class.

How to create a fully Encapsulation class in java?

By making all the data members of the class as private. we are making public setter and getter methods, in the class to set and get the data.

The Java Entity class (Bean class), is a fully encapsulated class in java.

Advantage of Encapsulation in Java.

There are many advantages of Encapsulation in java.

Make read-only and write-only classes using encapsulation.
Achieve data hiding.
The encapsulated classes are better for unit testing.
Easy and fast.
Control over data.

Java Simple Example of Encapsulation in Java

//A Java class which is a fully encapsulated class. 
package com.technicalround;

public class Employee {
// private data member
private Integer id;
private String name;
private String email;

// public getter method for name
public Integer getId() {
return id;
}

public String getName() {
return name;
}

public String getEmail() {
return email;
}

// public setter method for name
public void setName(String name){ 
this.name=name; 
}

public void setId(Integer id) {
this.id = id;
}


public void setEmail(String email) {
this.email = email;
}

@Override
public String toString() {
return "Employee [id=" + id + ", name=" + name + ", email=" + email + "]";
}

}

Test.java

package com.technicalround;

class Test {
public static void main(String[] args) {
// creating instance of the encapsulated class
Employee emp = new Employee();

// setting value in member
emp.setId(1);
emp.setName("Niraj");
emp.setName("niraj@gmail.com");

// getting the value of a member
System.out.println(emp.getId);
System.out.println(emp.getName());
System.out.println(emp.getEmail());
}
}

Output:

1
Niraj
niraj@gmail.com

How to create a read-only class in java?

Make all data members(Variable) as private in java class. No setter methods, so not able to change data members, only the getter method for getting data, from another class, then this class automatically becomes a read-only class.

All data members(Variable) as private
No setter methods
Only the getter method for getting data

Read-Only class Java Programming Example.

package com.testing;

public class Employee {
// private data member
private String name;

// public getter method for name
public String getName() {
return name;
}
}

In the above example, we are not providing the setter method, so it can not be able to change from other classes.

How to create a write-only class in java?

Make all data members(Variable) as private in java class. No getter methods, so not able to get data members from others class, only the setter method for changing data, from another class, then this class automatically becomes a write-only class.

All data members(Variable) as private
No getter methods
Only the setting method for changing data

Write-Only class Java Programming Example.

package com.testing;

public class Employee {
// private data member
private String name;

// public setter method for name
public void setName(String name) {
this.name = name;
}
}

In the above example, we are not providing the getter method. Therefore, we won’t be able to read data from other classes.

Example Program.

//A Java class which is a fully encapsulated class. 
package com.technicalround;

public class User {
// private data member
private Integer id;
private String name;
private String email;
private String phoneNo;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getEmail() {
return email;
}

public void setEmail(String email) {
this.email = email;
}

public String getPhoneNo() {
return phoneNo;
}

public void setPhoneNo(String phoneNo) {
this.phoneNo = phoneNo;
}

@Override
public String toString() {
return "User [id=" + id + ", name=" + name + ", email=" + email + ", phoneNo=" + phoneNo + "]";
}

}

Java test class

package com.technicalround;

class Test {
public static void main(String[] args) {
// creating instance of the encapsulated class
User user = new User();

// setting value in member
user.setName(1);
user.setName("Niraj");
user.setName("niraj@gmail.com");
user.setPhoneNo("9988776655");

// getting the value of a member
System.out.println(user.getId);
System.out.println(user.getName());
System.out.println(user.getEmail());
System.out.println(user.getPhoneNo());
}
}

Output:

1
Niraj
niraj@gmail.com
9988776655

Different between Encapsulation and Abstraction.

Both Encapsulation and Abstraction are two of the four basic OOP concepts. Both are used for hiding data, but they hide the data in different ways. Sometimes we are confused between both of them.

Abstraction deals with “What” to hides. Encapsulation deals with “How” to hides.
Abstraction hides the complex functionalities. Encapsulation binds the functionalities.
Abstraction solves the problem at the design level. Encapsulation solves its implementation level.
Abstraction focus on the outer lookout. Encapsulation focuses on internal working(inner lookout).
Abstraction is about hiding unwanted details. Encapsulation means hiding the code and data into a single unit

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