Pair.java

package folioxml.core;

public class Pair<A, B> {

    private final A first;
    private final B second;

    public Pair(A first, B second) {
        this.first = first;
        this.second = second;
    }

    public A getFirst() {
        return first;
    }

    public B getSecond() {
        return second;
    }

    public String toString() {
        return "(" + first + ", " + second + ")";
    }

    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 &&
                        Pair.equals(first, ((Pair) other).first) &&
                        Pair.equals(second, ((Pair) other).second);

    }

    public int hashCode() {
        if (first == null) return (second == null) ? 0 : second.hashCode() + 1;
        else if (second == null) return first.hashCode() + 2;
        else return first.hashCode() * 17 + second.hashCode();
    }

    public static <A, B> Pair<A, B> of(A a, B b) {
        return new Pair<A, B>(a, b);
    }

}