what is encapsulation java

Encapsulation in Java is a mechanism to wrap up variables and methods together
as a single unit. It is the process of hiding information details and protecting
data and behavior of the object. It is one of the four important OOP concepts. 
 The encapsulate class is easy to test, so it is also better for unit testing.

// Java program to demonstrate encapsulation 
public class Encapsulate 
{ 
    // private variables declared  
    // these can only be accessed by  
    // public methods of class 
    private String geekName; 
    private int geekRoll; 
    private int geekAge; 
  
    // get method for age to access  
    // private variable geekAge 
    public int getAge() { 
      return geekAge; 
    } 
   
    // get method for name to access  
    // private variable geekName 
    public String getName() { 
      return geekName; 
    } 
      
    // get method for roll to access  
    // private variable geekRoll 
    public int getRoll() { 
       return geekRoll; 
    } 
   
    // set method for age to access  
    // private variable geekage 
    public void setAge( int newAge) { 
      geekAge = newAge; 
    } 
   
    // set method for name to access  
    // private variable geekName 
    public void setName(String newName) { 
      geekName = newName; 
    } 
      
    // set method for roll to access  
    // private variable geekRoll 
    public void setRoll( int newRoll) { 
      geekRoll = newRoll; 
    } 
} 

public class TestEncapsulation {     
    public static void main (String[] args) { 
        Encapsulate obj = new Encapsulate(); 
          
        // setting values of the variables  
        obj.setName("Harsh"); 
        obj.setAge(19); 
        obj.setRoll(51); 
          
        // Displaying values of the variables 
        System.out.println("Geek's name: " + obj.getName()); 
        System.out.println("Geek's age: " + obj.getAge()); 
        System.out.println("Geek's roll: " + obj.getRoll()); 
          
        // Direct access of geekRoll is not possible 
        // due to encapsulation 
        // System.out.println("Geek's roll: " + obj.geekName);         
    } 
}