Is using the keywords static final sufficient to ensure object immutability?

Using the keywords static final in Java guarantees that the reference to the object will not change (final) and that the field belongs to the class, not an instance (static). However, this does not ensure the immutability of the object itself that the field refers to. If the object is mutable (for example, a collection or a regular object with setters), its internal state can be changed.

To create a truly immutable object:

• Make the class immutable, for example, declare all fields as private final.
• Do not provide methods that modify the object's state.
• If the fields are references to mutable objects, create copies of them when passing and returning.

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; }
}

Thus, static final is only part of the mechanism, but not sufficient to ensure the immutability of an object.