Selenium automation testing course with Java-Encapsulation in Java- class 14

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Encapsulation in Java
=====================
Encapsulation is one of the fundamental principles of Object-Oriented Programming (OOP) in Java.
It is the process of wrapping data (variables) and code (methods) together as a single unit and restricting direct access to some of the object’s components.

Definition:
==========
Encapsulation is the mechanism of hiding the internal state of an object and only exposing a controlled interface (via public methods).

Main Goals of Encapsulation:
============================
-Protect the data from unauthorized access (data hiding).
-Control how data is accessed or modified.
-Improve code maintainability, flexibility, and reusability.

How to Achieve Encapsulation in Java?
Encapsulation in Java is typically achieved by following these steps:
1 Declare variables as private inside a class to restrict direct access.
2 Provide public getter and setter methods to access and update the value of private variables.

Encapsulation Example:
=====================
public class Student {
// Step 1: Private data members
private String name;
private int age;

// Step 2: Public getter and setter methods
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 greater than 0) { // Adding some validation
this.age = age;
}
}
}
Usage:
public class Main {
public static void main(String[] args) {
Student s = new Student();
s.setName("John");
s.setAge(20);

System.out.println("Name: " + s.getName());
System.out.println("Age: " + s.getAge());
}
}
Why Encapsulation Matters?
Benefit Explanation
Security Prevents external code from directly modifying fields.
Validation Setters allow checking values before assignment.
Modularity Keeps code organized and easier to manage.
Flexibility You can change the internal implementation without affecting users of the class.
Without Encapsulation (Poor Practice):
public class Student {
public String name; // No control, bad practice
public int age;
}
Anyone can access and modify name and age directly, even with invalid values like age = -5.

Real-World Analogy:
===================
Think of a capsule (medicine) — the internal content (drug) is hidden and protected by the capsule shell. You only interact with the capsule, not the raw contents. Similarly, in encapsulation, you interact with methods — not the raw data.

Summary:
Concept Description
Encapsulation - Binding data and methods together while restricting direct access.
Access Modifiers- private, public, protected — used to control access.
Getter/Setter - Public methods to safely access private fields.
What is an Object class in Java?
In Java, the Object class is the root (or superclass) of all classes.
Every class in Java implicitly extends the java.lang.Object class, either directly or indirectly.
This means every object you create in Java inherits methods from the Object class.

Why is Object Class Important?
Common Functionality: It provides common methods like toString(), equals(), hashCode(), etc., that every Java object can use or override.

Polymorphism: Since all objects are instances of Object, you can write general-purpose methods that accept Object parameters and work with any object type.

Collection Framework: Many Java collections (like ArrayList, HashMap) store and manipulate elements as Object.

It is available in the package which is java.lang;
You don't need to import it explicitly because java.lang is automatically imported.

Key Methods of Object Class
Method Description
1 public String toString() Returns a string representation of the object.
2 public boolean equals(Object obj) Compares this object with another for equality.
3 public int hashCode() Returns an integer hash code for the object.
4 protected Object clone() Creates and returns a copy of the object (requires Cloneable interface).
5 public final Class? getClass() Returns the runtime class of the object.
6 protected void finalize() Called by garbage collector before object is destroyed (deprecated).
7 public final void wait() Causes current thread to wait until another thread calls
8 public final void wait(long timeout) final Waits for the specified time or until notified.
9 public final void wait(long timeout, int nanos) final Waits for the specified time in nanoseconds.
10 public final void notify() Wakes up a single thread waiting on this object's monitor.
11 public final void notifyAll()

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