cryptic comment in jdk source: // HD, Section 2-1

Question

i just stumbled onto this comment.

    public static int lowestOneBit(int i) {
    // HD, Section 2-1
    return i & -i;
    }

in the 1.5 java source. what does this comment mean? is it a reference to a book? a spec?

Answer 1

HD probably refers to Hacker's Delight by Henry S. Warren. Indeed, this formula appears on page 11, section 2-1.