Why might immutable objects be needed in practice?

• Thread Safety: Immutable objects are inherently thread-safe because their state cannot be changed after creation. This simplifies concurrent programming by avoiding data races.
• Simplicity: The object's state is fixed, reducing system complexity and making reasoning about its behavior easier.
• Caching: Since the object does not change, its hash code remains constant. This makes immutable objects ideal keys in HashMap or elements in HashSet, improving collection operation efficiency.
• Security: Returning immutable objects from methods guarantees that their internal state cannot be accidentally or maliciously altered by external code.
• Shared Usage: Immutable objects can be safely shared across multiple parts of an application without the need to create copies, saving memory.

Example of an immutable class in Java:

// Immutable class
public final class Point {

    private final int x;
    private final int y;

    public Point(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return x;
    }

    public int getY() {
        return y;
    }

    // No setters
    // No methods that modify state
}