Java 中 Pair 类的五种替代方案

谁践踏了优雅 2023-10-04 15:37 39阅读 0赞

Pair 是一个容器，用于存储两个对象的元组。Java 并没有真正提供 Pair 类的任何实现。这篇文章将讨论 Java 中 Pair 类的各种替代方案。

Pair 通常用于一起跟踪两个对象。它包含两个字段，通常称为`first`and `second`，能够存储任何内容。尽管`first`和`second`字段之间没有任何有意义的关系，但程序员经常会错过 Java 中的这个功能。

在上[一篇文章中][Link 1]，我们讨论了如何在 Java 中实现我们自己的 Pair 类。这篇文章将讨论 Java 中可用的解决方法来填补所需的空白，如下所述：

### 1. 使用`Map.Entry<K,V>`界面 ###

我们可以在 Java 中使用[Map.Entry<K,V>][Map.Entry_K_V]接口，类似于`std::pair`C++ 中的接口。这是具有代表键值对的有意义名称的绝佳示例。

为了创建表示从指定键到指定值的映射的条目，Java 提供了该`Map.Entry`接口的两个具体实现，即`AbstractMap.SimpleEntry`和`AbstractMap.SimpleImmutableEntry`。

[下载][Link 2] [运行代码][Link 3]

**输出：**  
  
\[Java=50，C++=30\]  
50

### 2. 使用 Java 8 – `javafx.util.Pair` ###

终于，经过漫长的等待，Java 8 的package.json 中添加了一个[Pair<K,V> 类][Pair_K_V_]`javafx.util`。类表示键值对，并支持像非常基本的操作`getKey()`，`getValue()`，`hashCode()`，`equals(java.lang.Object o)`，和`toString()`并具有继承一些方法`java.lang.Object`类。嗯，有总比没有好，是吧？

[下载代码][Link 4]

**输出：**  
  
\{C, 20\}  
\{C++, 30\}

### 3. 使用 Apache Commons Lang ###

Apache Commons Lang 库还提供了一个[Pair<L,R> 实用程序类，][Pair_L_R_]其元素是`left`和`right`。它被定义为抽象并实现了`Map.Entry`接口，其中键是`left`，值是`right`。

它具有`Pair.of()`可用于从指定的对象对中获取不可变对的方法。它的子类`MutablePair`是可变的，而不可变的`ImmutablePair`。但是，存储在`ImmutablePair`can中的对象的类型本身可能是可变的。

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      <span style="color:#444444;"><span style="color:#000000;"><span style="color:#800080;">import</span> <span style="color:#002d7a;">org</span><span style="color:#333333;">.</span><span style="color:#002d7a;">apache</span><span style="color:#333333;">.</span><span style="color:#002d7a;">commons</span><span style="color:#333333;">.</span><span style="color:#002d7a;">lang3</span><span style="color:#333333;">.</span><span style="color:#002d7a;">tuple</span><span style="color:#333333;">.</span><span style="color:#002d7a;">ImmutablePair</span><span style="color:#333333;">;</span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;"><span style="color:#800080;">import</span> <span style="color:#002d7a;">org</span><span style="color:#333333;">.</span><span style="color:#002d7a;">apache</span><span style="color:#333333;">.</span><span style="color:#002d7a;">commons</span><span style="color:#333333;">.</span><span style="color:#002d7a;">lang3</span><span style="color:#333333;">.</span><span style="color:#002d7a;">tuple</span><span style="color:#333333;">.</span><span style="color:#002d7a;">MutablePair</span><span style="color:#333333;">;</span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;"><span style="color:#800080;">import</span> <span style="color:#002d7a;">org</span><span style="color:#333333;">.</span><span style="color:#002d7a;">apache</span><span style="color:#333333;">.</span><span style="color:#002d7a;">commons</span><span style="color:#333333;">.</span><span style="color:#002d7a;">lang3</span><span style="color:#333333;">.</span><span style="color:#002d7a;">tuple</span><span style="color:#333333;">.</span><span style="color:#002d7a;">Pair</span><span style="color:#333333;">;</span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;">&nbsp;</span></span> 
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      <span style="color:#444444;"><span style="color:#000000;"><span style="color:#800080;">import</span> <span style="color:#002d7a;">java</span><span style="color:#333333;">.</span><span style="color:#002d7a;">util</span><span style="color:#333333;">.</span><span style="color:#002d7a;">ArrayList</span><span style="color:#333333;">;</span></span></span> 
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     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;"><span style="color:#800080;">import</span> <span style="color:#002d7a;">java</span><span style="color:#333333;">.</span><span style="color:#002d7a;">util</span><span style="color:#333333;">.</span><span style="color:#002d7a;">List</span><span style="color:#333333;">;</span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;"><span style="color:#800080;">class</span> <span style="color:#004ed0;">Main</span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;"><span style="color:#333333;">{ </span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#008200;">// Demonstrate Pair class provided Apache Commons Library in Java</span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#800080;">public</span> <span style="color:#800080;">static</span> <span style="color:#800080;">void</span> <span style="color:#004ed0;">main</span><span style="color:#333333;">(</span><span style="color:#800080;">String</span><span style="color:#333333;">[</span><span style="color:#333333;">]</span> <span style="color:#002d7a;">args</span><span style="color:#333333;">)</span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#333333;">{ </span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">List</span><span style="color:#006fe0;">&lt;</span><span style="color:#002d7a;">Pair</span><span style="color:#006fe0;">&lt;</span><span style="color:#800080;">String</span><span style="color:#333333;">,</span> <span style="color:#800080;">Integer</span><span style="color:#006fe0;">&gt;&gt;</span> <span style="color:#002d7a;">entries</span> <span style="color:#006fe0;">=</span> <span style="color:#800080;">new</span> <span style="color:#002d7a;">ArrayList</span><span style="color:#006fe0;">&lt;&gt;</span><span style="color:#333333;">(</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;">&nbsp;</span></span> 
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      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">entries</span><span style="color:#333333;">.</span><span style="color:#004ed0;">add</span><span style="color:#333333;">(</span><span style="color:#800080;">new</span> <span style="color:#002d7a;">MutablePair</span><span style="color:#006fe0;">&lt;&gt;</span><span style="color:#333333;">(</span><span style="color:#880000;">"C"</span><span style="color:#333333;">,</span> <span style="color:#ce0000;">20</span><span style="color:#333333;">)</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#008200;">// using `MutablePair`</span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">entries</span><span style="color:#333333;">.</span><span style="color:#004ed0;">add</span><span style="color:#333333;">(</span><span style="color:#800080;">new</span> <span style="color:#002d7a;">ImmutablePair</span><span style="color:#006fe0;">&lt;&gt;</span><span style="color:#333333;">(</span><span style="color:#880000;">"C++"</span><span style="color:#333333;">,</span> <span style="color:#ce0000;">30</span><span style="color:#333333;">)</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span>&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#008200;">// using `ImmutablePair`</span></span></span> 
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      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">entries</span><span style="color:#333333;">.</span><span style="color:#004ed0;">add</span><span style="color:#333333;">(</span><span style="color:#002d7a;">Pair</span><span style="color:#333333;">.</span><span style="color:#004ed0;">of</span><span style="color:#333333;">(</span><span style="color:#880000;">"Java"</span><span style="color:#333333;">,</span> <span style="color:#ce0000;">50</span><span style="color:#333333;">)</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span>&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#008200;">// using `Pair.of()`</span></span></span> 
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     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;</span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">System</span><span style="color:#333333;">.</span><span style="color:#002d7a;">out</span><span style="color:#333333;">.</span><span style="color:#004ed0;">println</span><span style="color:#333333;">(</span><span style="color:#002d7a;">entries</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;</span></span> 
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      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#008200;">// 1. The first pair is mutable</span></span></span> 
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     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">Pair</span><span style="color:#006fe0;">&lt;</span><span style="color:#800080;">String</span><span style="color:#333333;">,</span> <span style="color:#800080;">Integer</span><span style="color:#006fe0;">&gt;</span> <span style="color:#002d7a;">pair</span> <span style="color:#006fe0;">=</span> <span style="color:#002d7a;">entries</span><span style="color:#333333;">.</span><span style="color:#004ed0;">get</span><span style="color:#333333;">(</span><span style="color:#ce0000;">0</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">pair</span><span style="color:#333333;">.</span><span style="color:#004ed0;">setValue</span><span style="color:#333333;">(</span><span style="color:#ce0000;">100</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span> &nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#008200;">// works fine</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;</span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#008200;">// printing pair using `getKey()` and `getValue()` method</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">System</span><span style="color:#333333;">.</span><span style="color:#002d7a;">out</span><span style="color:#333333;">.</span><span style="color:#004ed0;">println</span><span style="color:#333333;">(</span><span style="color:#002d7a;">pair</span><span style="color:#333333;">.</span><span style="color:#004ed0;">getKey</span><span style="color:#333333;">(</span><span style="color:#333333;">)</span> <span style="color:#006fe0;">+</span> <span style="color:#880000;">", "</span> <span style="color:#006fe0;">+</span> <span style="color:#002d7a;">pair</span><span style="color:#333333;">.</span><span style="color:#004ed0;">getValue</span><span style="color:#333333;">(</span><span style="color:#333333;">)</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;</span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#008200;">// 2. The second pair is immutable</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">pair</span> <span style="color:#006fe0;">=</span> <span style="color:#002d7a;">entries</span><span style="color:#333333;">.</span><span style="color:#004ed0;">get</span><span style="color:#333333;">(</span><span style="color:#ce0000;">1</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#800080;">try</span> <span style="color:#333333;">{ </span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">pair</span><span style="color:#333333;">.</span><span style="color:#004ed0;">setValue</span><span style="color:#333333;">(</span><span style="color:#ce0000;">100</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span> <span style="color:#008200;">// runtime error</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#333333;">}</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#800080;">catch</span> <span style="color:#333333;">(</span><span style="color:#004ed0;">UnsupportedOperationException </span><span style="color:#002d7a;">ex</span><span style="color:#333333;">)</span> <span style="color:#333333;">{ </span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">System</span><span style="color:#333333;">.</span><span style="color:#002d7a;">out</span><span style="color:#333333;">.</span><span style="color:#004ed0;">println</span><span style="color:#333333;">(</span><span style="color:#880000;">"UnsupportedOperationException thrown"</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#333333;">}</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;</span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#008200;">// printing pair using `getLeft()` and `getRight()` method</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">System</span><span style="color:#333333;">.</span><span style="color:#002d7a;">out</span><span style="color:#333333;">.</span><span style="color:#004ed0;">println</span><span style="color:#333333;">(</span><span style="color:#002d7a;">pair</span><span style="color:#333333;">.</span><span style="color:#004ed0;">getLeft</span><span style="color:#333333;">(</span><span style="color:#333333;">)</span> <span style="color:#006fe0;">+</span> <span style="color:#880000;">", "</span> <span style="color:#006fe0;">+</span> <span style="color:#002d7a;">pair</span><span style="color:#333333;">.</span><span style="color:#004ed0;">getRight</span><span style="color:#333333;">(</span><span style="color:#333333;">)</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;</span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#008200;">// 3. The third pair is also immutable</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">pair</span> <span style="color:#006fe0;">=</span> <span style="color:#002d7a;">entries</span><span style="color:#333333;">.</span><span style="color:#004ed0;">get</span><span style="color:#333333;">(</span><span style="color:#ce0000;">2</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#800080;">try</span> <span style="color:#333333;">{ </span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">pair</span><span style="color:#333333;">.</span><span style="color:#004ed0;">setValue</span><span style="color:#333333;">(</span><span style="color:#ce0000;">100</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span> <span style="color:#008200;">// runtime error</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#333333;">}</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#800080;">catch</span> <span style="color:#333333;">(</span><span style="color:#004ed0;">UnsupportedOperationException </span><span style="color:#002d7a;">ex</span><span style="color:#333333;">)</span> <span style="color:#333333;">{ </span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">System</span><span style="color:#333333;">.</span><span style="color:#002d7a;">out</span><span style="color:#333333;">.</span><span style="color:#004ed0;">println</span><span style="color:#333333;">(</span><span style="color:#880000;">"UnsupportedOperationException thrown"</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#333333;">}</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#002d7a;">System</span><span style="color:#333333;">.</span><span style="color:#002d7a;">out</span><span style="color:#333333;">.</span><span style="color:#004ed0;">println</span><span style="color:#333333;">(</span><span style="color:#002d7a;">pair</span><span style="color:#333333;">.</span><span style="color:#004ed0;">getLeft</span><span style="color:#333333;">(</span><span style="color:#333333;">)</span> <span style="color:#006fe0;">+</span> <span style="color:#880000;">", "</span> <span style="color:#006fe0;">+</span> <span style="color:#002d7a;">pair</span><span style="color:#333333;">.</span><span style="color:#004ed0;">getRight</span><span style="color:#333333;">(</span><span style="color:#333333;">)</span><span style="color:#333333;">)</span><span style="color:#333333;">;</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;">&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#333333;">}</span></span></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#444444;"><span style="color:#000000;"><span style="color:#333333;">}</span></span></span> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

[下载代码][Link 5]

**输出：**  
  
\[(C,20), (C++,30), (Java,50)\]  
C, 100  
UnsupportedOperationException 抛出  
C++, 30  
UnsupportedOperationException 抛出  
Java, 50

### 4. 使用`JavaTuples`库 ###

[Javatuples][]是另一个处理元组的著名且简单的 Java 库。它提供了一组`Java`从一到十个元素的元组类。为了达到我们的目的，我们可以使用[Pair<A,B> 类][Pair_A_B_]。

[下载代码][Link 6]

**输出：**  
  
\{Java，50\}  
\{C++，30\}

### 五、使用`Collections.singletonMap()`方法 ###

另一种方法是`Collections.singletonMap()`在 Java 中使用类似于`Map.Entry<K,V>`前面讨论的 。它返回一个不可变的单例映射，只包含指定的键值对映射，可以将其视为 Pair。

[下载][Link 7] [运行代码][Link 8]

**输出：**  
  
\[\{Java=50\}，\{C++=30\}\]

最后，在Android项目中，我们可以使用Android SDK提供的[android.util.Pair][]类。

这就是`Pair`Java 类的替代方案。

[Link 1]: https://www.techiedelight.com/implement-pair-class-java/
[Map.Entry_K_V]: https://docs.oracle.com/javase/8/docs/api/java/util/Map.Entry.html
[Link 2]: https://www.techiedelight.com/code/yZnTs2
[Link 3]: https://techiedelight.com/compiler/?run=yZnTs2
[Pair_K_V_]: https://docs.oracle.com/javafx/2/api/javafx/util/Pair.html
[Link 4]: https://www.techiedelight.com/code/A7i9ml
[Pair_L_R_]: https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/tuple/Pair.html
[Link 5]: https://www.techiedelight.com/code/gV09or
[Javatuples]: http://www.javatuples.org/
[Pair_A_B_]: https://www.techiedelight.com/javatuples-library-use-org-javatuples-pair-class/
[Link 6]: https://www.techiedelight.com/code/HkD9kH
[Link 7]: https://www.techiedelight.com/code/GhBCpW
[Link 8]: https://techiedelight.com/compiler/?run=GhBCpW
[android.util.Pair]: https://developer.android.com/reference/android/util/Pair.html