Java计算两个数组之间的并集

一时失言乱红尘 2023-10-04 10:54 19阅读 0赞

学习使用[HashSet][]类在Java中查找**两个[数组][Link 1]****之间**的**并集**。在集合论中，集合集合的[并集][Link 2]（用U表示）是集合中所有元素的集合。

例如，两个集合A和B的并集是A，B或A和B中所有元素的集合。

![联盟][2c586050ed23c80010f7e75ed12d9752.png]

并集

要获得两个数组的并集，请按照下列步骤操作：

1.  在HashSet实例中推送第一个数组。
2.  使用**addAll（）**方法将第二个数组的元素添加到集合中。
3.  同样，将更多数组中的所有元素添加到集合中（如果有）。

### 1.两个整数数组之间的并集 ###

Java程序获取两个整数数组之间的联合并打印输出。

<table>  
 <span style="color:#212121;">Main.java</span>  
 <tbody> 
  <tr> 
   <td style="text-align:left;vertical-align:baseline;"> 
    <div style="margin-left:0px;"> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>import</code> <code>java.util.Arrays;</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>import</code> <code>java.util.HashSet;</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;">&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>public</code> <code>class</code> <code>Main </code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>{ </code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;</code><code>public</code> <code>static</code> <code>void</code> <code>main(String[] args) </code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;</code><code>{ </code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>Integer[] firstArray = { </code><code>0</code><code>,</code><code>2</code><code>,</code><code>4</code><code>,</code><code>6</code><code>,</code><code>8</code><code>};</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>Integer[] secondArray = { </code><code>1</code><code>,</code><code>3</code><code>,</code><code>5</code><code>,</code><code>7</code><code>,</code><code>9</code><code>};</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>HashSet&lt;Integer&gt; set = </code><code>new</code> <code>HashSet&lt;&gt;(); </code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>set.addAll(Arrays.asList(firstArray));</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>set.addAll(Arrays.asList(secondArray));</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>System.out.println(set);</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>//convert to array</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code><code>Integer[] union = {};</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>union = set.toArray(union);</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>System.out.println(Arrays.toString(union));</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;</code><code>}</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>}</code></span> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

程序输出。

### 2.两个字符串数组之间的并集 ###

Java程序获取两个字符串数组之间的联合并打印输出。

<table>  
 <span style="color:#212121;">Main.java</span>  
 <tbody> 
  <tr> 
   <td style="text-align:left;vertical-align:baseline;"> 
    <div style="margin-left:0px;"> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>import</code> <code>java.util.Arrays;</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>import</code> <code>java.util.HashSet;</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;">&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>public</code> <code>class</code> <code>Main </code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>{ </code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;</code><code>public</code> <code>static</code> <code>void</code> <code>main(String[] args) </code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;</code><code>{ </code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>String[] firstArray = { </code><code>"A"</code><code>, </code><code>"B"</code><code>, </code><code>"C"</code><code>, </code><code>"D"</code><code>};</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>String[] secondArray = { </code><code>"D"</code><code>, </code><code>"A"</code><code>, </code><code>"E"</code><code>, </code><code>"F"</code><code>};</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>HashSet&lt;String&gt; set = </code><code>new</code> <code>HashSet&lt;&gt;(); </code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>set.addAll(Arrays.asList(firstArray));</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>set.addAll(Arrays.asList(secondArray));</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>System.out.println(set);</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>//convert to array</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>String[] union = {};</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>union = set.toArray(union);</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code>&nbsp;</span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>System.out.println(Arrays.toString(union));</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>&nbsp;&nbsp;</code><code>}</code></span> 
     </div> 
     <div style="margin-left:0px;"> 
      <span style="color:#212121;"><code>}</code></span> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

程序输出。

学习愉快！

[HashSet]: https://howtodoinjava.com/java/collections/java-hashset/
[Link 1]: https://howtodoinjava.com/java-array/
[Link 2]: https://en.wikipedia.org/wiki/Union_%28set_theory%29
[2c586050ed23c80010f7e75ed12d9752.png]: https://img-blog.csdnimg.cn/img_convert/2c586050ed23c80010f7e75ed12d9752.png