? Immutable Collections in Advance Java

? Quick Overview

Immutable Collections are collections whose contents cannot be changed after creation. In Java, immutable collections were officially introduced in Java 9 using factory methods. They improve safety, readability, and performance in modern Java applications.

? Key Concepts

• Immutable means no add, remove, or update operations allowed
• Available for List, Set, and Map
• Thread-safe by design
• Introduced in Java 9 using of() methods

? Syntax / Theory

Java provides static factory methods to create immutable collections. Once created, any attempt to modify them throws UnsupportedOperationException.

• List.of(elements)
• Set.of(elements)
• Map.of(key, value)

? Code Example(s)

// Creating an immutable List using Java 9+
import java.util.List;

public class ImmutableListDemo {
public static void main(String[] args) {
List names = List.of("Java", "Python", "C++");
System.out.println(names);
}
}

// Attempting to modify immutable collection causes exception
import java.util.List;

public class ModifyImmutable {
public static void main(String[] args) {
List nums = List.of(1, 2, 3);
nums.add(4);
}
}

? Interactive Simulation

Try adding elements to see the difference!

? Live Output / Explanation