java pair提高效率

public class Pair<A, B>

{

    public final A fst;

    public final B snd;

    public Pair(A fst, B snd)

    {

        this.fst = fst;

        this.snd = snd;

    }

    public String toString()

    {

        return "Pair[" + fst + "," + snd + "]";

    }

    private static boolean equals(Object x, Object y)

    {

        return (x == null && y == null) || (x != null && x.equals(y));

    }

    public boolean equals(Object other)

    {

        return other instanceof Pair<?, ?> && equals(fst, ((Pair<?, ?>)other).fst)

            && equals(snd, ((Pair<?, ?>)other).snd);

    }

    public int hashCode()

    {

        if (fst == null)

            return (snd == null) ? 0 : snd.hashCode() + 1;

        else if (snd == null)

            return fst.hashCode() + 2;

        else

            return fst.hashCode() * 17 + snd.hashCode();

    }

    public static <A, B> Pair<A, B> of(A a, B b)

    {

        return new Pair<A, B>(a, b);

    }

}