为了方便起见，以下是一些具有多级元组的库:

JavaTuples。它只有1-10度的元组。 JavaSlang。0-8度的元组和许多其他功能性的东西。 jOOλ。0-16度的元组和其他一些功能性的好东西。(免责声明，我在维修公司工作) Functional Java。0-8度的元组和许多其他功能性的东西。

已经提到的其他库至少包含Pair元组。

具体来说，在函数式编程的上下文中，它使用了大量的结构类型，而不是名义类型(正如公认答案中提倡的那样)，这些库及其元组非常方便。

简单的方法Object[] -可以作为一个几何体元组使用

我注意到所有的Pair实现都散布在这里，属性含义取决于两个值的顺序。当我想到一对时，我想到的是两件物品的组合，这两件物品的顺序不重要。下面是我对一个无序对的实现，使用hashCode和equals重写以确保集合中的期望行为。也可克隆。

/**
 * The class <code>Pair</code> models a container for two objects wherein the
 * object order is of no consequence for equality and hashing. An example of
 * using Pair would be as the return type for a method that needs to return two
 * related objects. Another good use is as entries in a Set or keys in a Map
 * when only the unordered combination of two objects is of interest.<p>
 * The term "object" as being a one of a Pair can be loosely interpreted. A
 * Pair may have one or two <code>null</code> entries as values. Both values
 * may also be the same object.<p>
 * Mind that the order of the type parameters T and U is of no importance. A
 * Pair&lt;T, U> can still return <code>true</code> for method <code>equals</code>
 * called with a Pair&lt;U, T> argument.<p>
 * Instances of this class are immutable, but the provided values might not be.
 * This means the consistency of equality checks and the hash code is only as
 * strong as that of the value types.<p>
 */
public class Pair<T, U> implements Cloneable {

    /**
     * One of the two values, for the declared type T.
     */
    private final T object1;
    /**
     * One of the two values, for the declared type U.
     */
    private final U object2;
    private final boolean object1Null;
    private final boolean object2Null;
    private final boolean dualNull;

    /**
     * Constructs a new <code>Pair&lt;T, U&gt;</code> with T object1 and U object2 as
     * its values. The order of the arguments is of no consequence. One or both of
     * the values may be <code>null</code> and both values may be the same object.
     *
     * @param object1 T to serve as one value.
     * @param object2 U to serve as the other value.
     */
    public Pair(T object1, U object2) {

        this.object1 = object1;
        this.object2 = object2;
        object1Null = object1 == null;
        object2Null = object2 == null;
        dualNull = object1Null && object2Null;

    }

    /**
     * Gets the value of this Pair provided as the first argument in the constructor.
     *
     * @return a value of this Pair.
     */
    public T getObject1() {

        return object1;

    }

    /**
     * Gets the value of this Pair provided as the second argument in the constructor.
     *
     * @return a value of this Pair.
     */
    public U getObject2() {

        return object2;

    }

    /**
     * Returns a shallow copy of this Pair. The returned Pair is a new instance
     * created with the same values as this Pair. The values themselves are not
     * cloned.
     *
     * @return a clone of this Pair.
     */
    @Override
    public Pair<T, U> clone() {

        return new Pair<T, U>(object1, object2);

    }

    /**
     * Indicates whether some other object is "equal" to this one.
     * This Pair is considered equal to the object if and only if
     * <ul>
     * <li>the Object argument is not null,
     * <li>the Object argument has a runtime type Pair or a subclass,
     * </ul>
     * AND
     * <ul>
     * <li>the Object argument refers to this pair
     * <li>OR this pair's values are both null and the other pair's values are both null
     * <li>OR this pair has one null value and the other pair has one null value and
     * the remaining non-null values of both pairs are equal
     * <li>OR both pairs have no null values and have value tuples &lt;v1, v2> of
     * this pair and &lt;o1, o2> of the other pair so that at least one of the
     * following statements is true:
     * <ul>
     * <li>v1 equals o1 and v2 equals o2
     * <li>v1 equals o2 and v2 equals o1
     * </ul>
     * </ul>
     * In any other case (such as when this pair has two null parts but the other
     * only one) this method returns false.<p>
     * The type parameters that were used for the other pair are of no importance.
     * A Pair&lt;T, U> can return <code>true</code> for equality testing with
     * a Pair&lt;T, V> even if V is neither a super- nor subtype of U, should
     * the the value equality checks be positive or the U and V type values
     * are both <code>null</code>. Type erasure for parameter types at compile
     * time means that type checks are delegated to calls of the <code>equals</code>
     * methods on the values themselves.
     *
     * @param obj the reference object with which to compare.
     * @return true if the object is a Pair equal to this one.
     */
    @Override
    public boolean equals(Object obj) {

        if(obj == null)
            return false;

        if(this == obj)
            return true;

        if(!(obj instanceof Pair<?, ?>))
            return false;

        final Pair<?, ?> otherPair = (Pair<?, ?>)obj;

        if(dualNull)
            return otherPair.dualNull;

        //After this we're sure at least one part in this is not null

        if(otherPair.dualNull)
            return false;

        //After this we're sure at least one part in obj is not null

        if(object1Null) {
            if(otherPair.object1Null) //Yes: this and other both have non-null part2
                return object2.equals(otherPair.object2);
            else if(otherPair.object2Null) //Yes: this has non-null part2, other has non-null part1
                return object2.equals(otherPair.object1);
            else //Remaining case: other has no non-null parts
                return false;
        } else if(object2Null) {
            if(otherPair.object2Null) //Yes: this and other both have non-null part1
                return object1.equals(otherPair.object1);
            else if(otherPair.object1Null) //Yes: this has non-null part1, other has non-null part2
                return object1.equals(otherPair.object2);
            else //Remaining case: other has no non-null parts
                return false;
        } else {
            //Transitive and symmetric requirements of equals will make sure
            //checking the following cases are sufficient
            if(object1.equals(otherPair.object1))
                return object2.equals(otherPair.object2);
            else if(object1.equals(otherPair.object2))
                return object2.equals(otherPair.object1);
            else
                return false;
        }

    }

    /**
     * Returns a hash code value for the pair. This is calculated as the sum
     * of the hash codes for the two values, wherein a value that is <code>null</code>
     * contributes 0 to the sum. This implementation adheres to the contract for
     * <code>hashCode()</code> as specified for <code>Object()</code>. The returned
     * value hash code consistently remain the same for multiple invocations
     * during an execution of a Java application, unless at least one of the pair
     * values has its hash code changed. That would imply information used for 
     * equals in the changed value(s) has also changed, which would carry that
     * change onto this class' <code>equals</code> implementation.
     *
     * @return a hash code for this Pair.
     */
    @Override
    public int hashCode() {

        int hashCode = object1Null ? 0 : object1.hashCode();
        hashCode += (object2Null ? 0 : object2.hashCode());
        return hashCode;

    }

}

这个实现已经经过了适当的单元测试，并且在Set和Map中的使用已经经过了尝试。

请注意，我并没有要求在公共领域发布这个。这是我为在应用程序中使用而编写的代码，因此如果您打算使用它，请避免直接复制，并在注释和名称上搞得一团糟。明白我的意思吗?

Spring数据有一个Pair，可以像下面这样使用，

Pair<S, T> pair = Pair.of(S type data, T type data)

最大的问题可能是不能确保A和B上的不可变(参见如何确保类型参数是不可变的)，因此hashCode()在插入到集合后可能会为相同的Pair给出不一致的结果(这将给出未定义的行为，参见定义可变字段中的equals)。对于一个特定的(非泛型的)Pair类，程序员可以通过仔细选择a和B为不可变来确保不可变性。

不管怎样，从@PeterLawrey的回答中清除泛型的警告(java 1.7):

public class Pair<A extends Comparable<? super A>,
                    B extends Comparable<? super B>>
        implements Comparable<Pair<A, B>> {

    public final A first;
    public final B second;

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

    public static <A extends Comparable<? super A>,
                    B extends Comparable<? super B>>
            Pair<A, B> of(A first, B second) {
        return new Pair<A, B>(first, second);
    }

    @Override
    public int compareTo(Pair<A, B> o) {
        int cmp = o == null ? 1 : (this.first).compareTo(o.first);
        return cmp == 0 ? (this.second).compareTo(o.second) : cmp;
    }

    @Override
    public int hashCode() {
        return 31 * hashcode(first) + hashcode(second);
    }

    // TODO : move this to a helper class.
    private static int hashcode(Object o) {
        return o == null ? 0 : o.hashCode();
    }

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

    // TODO : move this to a helper class.
    private boolean equal(Object o1, Object o2) {
        return o1 == o2 || (o1 != null && o1.equals(o2));
    }

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

补充/更正非常欢迎:)特别是我不太确定我使用Pair<?, ? >。

有关为什么这种语法的更多信息，请参阅确保对象实现可比和详细解释如何在Java中实现一个通用的max(可比a，可比b)函数?

在我看来，Java中没有Pair，因为如果你想直接在Pair上添加额外的功能(例如Comparable)，你必须绑定类型。在c++中，我们不在乎，如果组成一个pair的类型没有操作符<，则pair::operator <也不会被编译。

Comparable的一个例子:

public class Pair<F, S> implements Comparable<Pair<? extends F, ? extends S>> {
    public final F first;
    public final S second;
    /* ... */
    public int compareTo(Pair<? extends F, ? extends S> that) {
        int cf = compare(first, that.first);
        return cf == 0 ? compare(second, that.second) : cf;
    }
    //Why null is decided to be less than everything?
    private static int compare(Object l, Object r) {
        if (l == null) {
            return r == null ? 0 : -1;
        } else {
            return r == null ? 1 : ((Comparable) (l)).compareTo(r);
        }
    }
}

/* ... */

Pair<Thread, HashMap<String, Integer>> a = /* ... */;
Pair<Thread, HashMap<String, Integer>> b = /* ... */;
//Runtime error here instead of compile error!
System.out.println(a.compareTo(b));

Comparable与编译时检查类型参数是否可比较的示例:

public class Pair<
        F extends Comparable<? super F>, 
        S extends Comparable<? super S>
> implements Comparable<Pair<? extends F, ? extends S>> {
    public final F first;
    public final S second;
    /* ... */
    public int compareTo(Pair<? extends F, ? extends S> that) {
        int cf = compare(first, that.first);
        return cf == 0 ? compare(second, that.second) : cf;
    }
    //Why null is decided to be less than everything?
    private static <
            T extends Comparable<? super T>
    > int compare(T l, T r) {
        if (l == null) {
            return r == null ? 0 : -1;
        } else {
            return r == null ? 1 : l.compareTo(r);
        }
    }
}

/* ... */

//Will not compile because Thread is not Comparable<? super Thread>
Pair<Thread, HashMap<String, Integer>> a = /* ... */;
Pair<Thread, HashMap<String, Integer>> b = /* ... */;
System.out.println(a.compareTo(b));

这很好，但是这次您不能在Pair中使用不可比较的类型作为类型参数。 你可能会在一些实用程序类中使用很多comparator for Pair，但是c++的人可能不会理解。另一种方法是在类型层次结构中编写很多类，在类型参数上有不同的边界，但是有太多可能的边界和它们的组合……