Encapsulation

Data hiding, access modifiers, getter/setter methods, and static members in Java.

Definition

Encapsulation is the practice of bundling data (fields) and the methods that operate on that data into a single class, while restricting direct access to the internal state.

Access Modifiers

Modifier	Class	Package	Subclass	World
`public`	Yes	Yes	Yes	Yes
`protected`	Yes	Yes	Yes	No
default	Yes	Yes	No	No
`private`	Yes	No	No	No

Getter and Setter Methods

Getters return the value of a private field.
Setters assign a value to a private field, optionally with validation.

Static Variables and Methods

static variables — Shared across all instances of a class.
static methods — Belong to the class rather than any instance. Called via ClassName.method().

Example

// EncapsulationDemo.java
// Demonstrates encapsulation using private variables and getter/setter methods.

class Person {
	// Private variables (data hiding)
	private String name;
	private int age;

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

	// Setter for name
	public void setName(String n) {
		name = n;
	}

	// Getter for age
	public int getAge() {
		return age;
	}

	// Setter for age
	public void setAge(int a) {
		age = a;
	}
}

public class EncapsulationDemo {
	public static void main(String[] args) {
		// Create Person object and set values
		Person p = new Person();
		p.setName("Bob");
		p.setAge(25);
		// Print details
		System.out.println(p.getName() + " is " + p.getAge() + " years old.");
	}
}

Full source: examples/06-encapsulation/EncapsulationDemo.java