What immutable objects do you know in Java?

In Java, immutable objects are objects whose state cannot be changed after creation. A classic example is the String class. Other well-known immutable objects:

• Wrappers for primitive types: Integer, Long, Double, Boolean, etc.
• Classes from the java.time package (e.g., LocalDate, LocalDateTime, Instant) that represent immutable dates and times.

To make a custom class immutable, you should:

• Make the class final or do not provide methods to modify the state.
• All fields should be private final.
• Do not provide setters.
• If fields are references to mutable objects, create copies when passing and returning.

Example of a simple 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; }
}