// Immutable User Class in Java (Enforce Immutability)
public class Main {
// Immutable User class
static final class User {
// Fields are private and final → cannot be modified after construction
private final int id;
private final String name;
// Constructor initializes all fields exactly once
public User(int id, String name) {
this.id = id;
this.name = name;
}
// Getter methods provide read‑only access
public int getId() {
return id;
}
public String getName() {
return name;
}
// No setters → immutability enforced
}
public static void main(String[] args) {
// Create an immutable User object
User u = new User(42, "James");
System.out.println("ID: " + u.getId());
System.out.println("Name: " + u.getName());
// The following lines would cause compile‑time errors:
// u.id = 100; // ERROR: id is final + private
// u.name = "John"; // ERROR: name is final + private
// u.setName("John"); // ERROR: no setter exists
// The object is fully immutable
}
}
/*
run:
ID: 42
Name: James
*/
