Which classes implement immutable objects in programming?

In Java, immutable objects are objects whose state cannot be changed after creation. Main classes implementing immutable objects:

• String — a class for strings, which cannot be changed after creation.
• Wrapper classes for primitives: Integer, Long, Double, Boolean, etc.
• BigInteger and BigDecimal — for working with large numbers and precise arithmetic.
• LocalDate, LocalDateTime, and other classes from the java.time package.

To create your own immutable class, you need to:

• Make the class final or do not provide methods to change the state.
• Make all fields private final.
• Do not provide setters.
• If fields are references to mutable objects, return their copies.

Example:

public final class ImmutablePoint {
    private final int x;
    private final int y;

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

    public int getX() { return x; }
    public int getY() { return y; }
}