What is the equivalent of the C++ Pair in Java?

Question

Is there a good reason why there is no Pair in Java? What would be the equivalent of this C++ construct? I would rather avoid reimplementing my own.<

Answer 1

How about http://www.javatuples.org/index.html I have found it very useful.

The javatuples offers you tuple classes from one to ten elements:

Unit<A> (1 element)
Pair<A,B> (2 elements)
Triplet<A,B,C> (3 elements)
Quartet<A,B,C,D> (4 elements)
Quintet<A,B,C,D,E> (5 elements)
Sextet<A,B,C,D,E,F> (6 elements)
Septet<A,B,C,D,E,F,G> (7 elements)
Octet<A,B,C,D,E,F,G,H> (8 elements)
Ennead<A,B,C,D,E,F,G,H,I> (9 elements)
Decade<A,B,C,D,E,F,G,H,I,J> (10 elements)

Answer 2

If anyone wants a dead-simple and easy to use version I made my available at https://github.com/lfac-pt/Java-Pair. Also, improvements are very much welcome!

Answer 3

com.sun.tools.javac.util.Pair is an simple implementation of a pair. It can be found in jdk1.7.0_51\lib\tools.jar.

Other than the org.apache.commons.lang3.tuple.Pair, it's not just an interface.

Answer 4

android provides Pairclass (http://developer.android.com/reference/android/util/Pair.html) , here the implementation:

public class Pair<F, S> {
    public final F first;
    public final S second;

    public Pair(F first, S second) {
        this.first = first;
        this.second = second;
    }

    @Override
    public boolean equals(Object o) {
        if (!(o instanceof Pair)) {
            return false;
        }
        Pair<?, ?> p = (Pair<?, ?>) o;
        return Objects.equal(p.first, first) && Objects.equal(p.second, second);
    }

    @Override
    public int hashCode() {
        return (first == null ? 0 : first.hashCode()) ^ (second == null ? 0 : second.hashCode());
    }

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

Answer 5

You can use Google's AutoValue library - https://github.com/google/auto/tree/master/value.

You create a very small abstract class and annotate it with @AutoValue and the annotation processor generates a concrete class for you that has a value semantic.

Answer 6

JavaFX (which comes bundled with Java 8) has the Pair< A,B > class