Java Encapsulation (get/set)

What is Encapsulation

The meaning of Encapsulation is to make sure that “sensitive” data is hidden from users. We know that private variables can only be accessed within the same class (an outside class has no access to it).

public class Person {

  // class attributes / class variables
  private String name; // private = restricted access

}

Why Encapsulation?

• Better control of class attributes / class variables and methods
• Class attributes can be made read-only (if you only use the get method), or write-only (if you only use the set method)
• Flexible: the programmer can change one part of the code without affecting other parts
• Increased security of data

How Encapsulation Works

So, we already know that private variables can only be accessed within the same class (an outside class has no access to it).

However, it is possible to access them if we provide public get and set methods.

public class Person {

  private String name; // private = restricted access

  // Getter
  public String getName() {

    return name;

  }

  // Setter
  public void setName(String newName) {
    
    this.name = newName; //this.name is point to Private String name ->lass attributes / class variables

  }

}

The get method returns the variable value, and the set method sets the value.

Syntax for both is that they start with either get or set, followed by the name of the variable, with the first letter in upper case:

The get method returns the value of the variable name.

The set method takes a parameter (newName) and assigns it to the name variable. The this keyword is used to refer to the current object.

However, as the name variable is declared as private, we cannot access it from outside this class:

public class Main {

  public static void main(String[] args) {

    Person myObj = new Person();

    myObj.name = "John";  // error, try to access private variable from the other class

    System.out.println(myObj.name); // error 

  }

//Output 
MyClass.java:4: error: name has private access in Person
    myObj.name = "John";
         ^
MyClass.java:5: error: name has private access in Person
    System.out.println(myObj.name);
                  ^
2 errors

Instead, we use the getName() and setName() methods to access and update the private variable:

public class Main {

  public static void main(String[] args) {

    Person myObj = new Person();

    myObj.setName("John"); // Set the value of the name variable to "John"

    System.out.println(myObj.getName());

  }

}

// Outputs "John"