Create 1.java

Author: M-F-Tushar

Exams/CT/CT-3/1.java

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+/*
+🧩 Definition of Encapsulation (in Java)
+
+Encapsulation is one of the main principles of Object-Oriented Programming (OOP).
+It means wrapping data (variables) and methods (functions) that operate on that data into a single unit — usually a class — and restricting direct access to some of the object’s components.
+
+In simple words:
+
+Encapsulation is the process of binding data and code together while hiding the internal details of how the data is stored or modified.
+
+🔒 Purpose of Encapsulation
+
+Encapsulation’s main goals are:
+
+Data Hiding:
+
+The object’s internal data is not directly accessible from outside the class.
+
+Only specific, controlled methods can access or modify it.
+
+This prevents accidental or unauthorized changes.
+
+Controlled Access via Getters and Setters:
+
+To access or modify private data safely, we use getter (to read) and setter (to write) methods.
+
+This allows us to validate or restrict values before assigning them.
+
+🧠 How Data Hiding Works
+
+In Java:
+
+You make instance variables private so they cannot be accessed directly from outside the class.
+
+You provide public methods (getters and setters) to get or set their values safely.
+*/
+✅ Example: Encapsulation in Java
+class Student {
+    // Private data (data hiding)
+    private String name;
+    private int age;
+
+    // Getter method for 'name'
+    public String getName() {
+        return name;
+    }
+
+    // Setter method for 'name'
+    public void setName(String newName) {
+        name = newName;
+    }
+
+    // Getter method for 'age'
+    public int getAge() {
+        return age;
+    }
+
+    // Setter method for 'age' with validation
+    public void setAge(int newAge) {
+        if (newAge > 0) {
+            age = newAge;
+        } else {
+            System.out.println("Age must be positive!");
+        }
+    }
+}
+
+public class Main {
+    public static void main(String[] args) {
+        Student s = new Student();
+
+        // Accessing private data using setter methods
+        s.setName("Alice");
+        s.setAge(20);
+
+        // Getting private data using getter methods
+        System.out.println("Name: " + s.getName());
+        System.out.println("Age: " + s.getAge());
+
+        // Trying to set invalid age
+        s.setAge(-5);
+    }
+}