What makes immutable objects safe to use in a multithreaded environment?

Immutable objects are safe for multithreaded environments because their state does not change after creation. This means that multiple threads can read data simultaneously without the risk of race conditions or the need for synchronization. Since the object is not modified, there are no issues with visibility of changes or partially updated states.

Example of an immutable class in Java:

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; }
}

Such an object can be safely used in multiple threads without additional synchronization.