Java Pair

Pair.java

public class Pair<U,T> {

    public final U left;
    public final T right;

    public static <U,T> Pair<U,T> of(U u, T t) {
        return new Pair<U,T>(u, t);
    }

    public Pair(U left, T right) {
        if (left == null) throw new IllegalArgumentException("left cannot be null");
        if (right == null) throw new IllegalArgumentException("right cannot be null");
        this.left = left;
        this.right = right;
    }

    @Override public int hashCode() {
        return 31 * left.hashCode() + right.hashCode();
    }

    @Override public boolean equals(Object obj) {
        if (this == obj) return true;

        if (obj == null ) return false;

        if (!(obj instanceof Pair)) return false;

        Pair p = (Pair) obj;

        return left.equals(p.left) && right.equals(p.right);
    }

    @Override public String toString() {
        return "Pair(" + left + "," + right + ")";
    }
}