What is encapsulation in Java and how is it implemented

Encapsulation is one of the fundamental principles of object-oriented programming (OOP) and is a mechanism for bundling data and the methods that operate on that data, into a single unit called a class. It is used to hide the internal state of an object and provide controlled access to that state through public methods. In Java, encapsulation is implemented using access modifiers and getter and setter methods.

Access Modifiers: Java provides four access modifiers that can be used to control the visibility of variables and methods:

1. private: Variables and methods declared as private are only accessible within the same class. They cannot be accessed from outside the class.

2. public: Variables and methods declared as public can be accessed from anywhere, including other classes and packages.

3. protected: Variables and methods declared as protected are accessible within the same class, subclasses, and classes in the same package.

4. Default (no modifier): If no access modifier is specified, it is considered as default. Variables and methods with default access are accessible within the same package only.

Getter and Setter Methods: Encapsulation encourages the use of getter and setter methods to access and modify the internal state (private variables) of an object. Getter methods are used to retrieve the values of private variables, and setter methods are used to modify the values of private variables.

By using getter and setter methods, we can control the access to the internal state of an object. These methods can include additional logic, such as validation or calculations, before allowing access to or modification of the data.

Here's an example to illustrate encapsulation in Java:

public class Person { private String name; private int age; public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { if (age >= 0) { this.age = age; } else { System.out.println("Invalid age value."); } } }

In the above example, the name and age variables are private, meaning they cannot be directly accessed from outside the Person class. To access or modify these variables, we use the public getter and setter methods (getName(), setName(), getAge(), setAge()). These methods provide controlled access to the internal state of the Person object and allow us to enforce any necessary validation or logic.

Encapsulation helps in maintaining the integrity of the object's data by preventing direct access to it and promoting the use of defined methods. It also provides a way to hide implementation details and protect sensitive data.