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  • [java] 求2个集合的交 差 并集

    要求2个集合的交 差 并集。

    set集合,如下

     1 import java.util.HashSet;
     2 import java.util.Set;
     3 
     4 public class SetTest {
     5     public static void main(String[] args) {
     6         Set<String> set1=new HashSet<String>();
     7         Set<String> set2=new HashSet<String>();
     8         Set<String> result=new HashSet<String>();
     9         
    10         set1.add("a");
    11         set1.add("b");
    12         set1.add("c");
    13         set1.add("e");
    14         set1.add("d");
    15         
    16         
    17         set2.add("a1");
    18         set2.add("b1");
    19         set2.add("c1");
    20         set2.add("e");
    21         set2.add("d");
    22         
    23         result.clear();
    24         result.addAll(set1);
    25         result.retainAll(set2);
    26         System.out.println("交集:"+result);
    27 
    28         result.clear();
    29         result.addAll(set1);
    30         result.removeAll(set2);
    31         System.out.println("差集:"+result);
    32 
    33         result.clear();
    34         result.addAll(set1);
    35         result.addAll(set2);
    36         System.out.println("并集:"+result);
    37         
    38     }
    39 }

    list集合方法相同,代码如下

     1 import java.util.ArrayList;
     2 import java.util.List;
     3 
     4 public class ListTest {
     5     public static void main(String[] args) {
     6         List<String> list1=new ArrayList<String>();
     7         List<String> list2=new ArrayList<String>();
     8         List<String> result=new ArrayList<String>();
     9         
    10         list1.add("a");
    11         list1.add("b");
    12         list1.add("c");
    13         list1.add("e");
    14         list1.add("d");
    15         
    16         
    17         list2.add("a1");
    18         list2.add("b1");
    19         list2.add("c1");
    20         list2.add("e");
    21         list2.add("d");
    22         
    23         result.clear();
    24         result.addAll(list1);
    25         result.retainAll(list2);
    26         System.out.println("交集:"+result);
    27 
    28         result.clear();
    29         result.addAll(list1);
    30         result.removeAll(list2);
    31         System.out.println("差集:"+result);
    32 
    33         result.clear();
    34         result.addAll(list1);
    35         result.addAll(list2);
    36         System.out.println("并集:"+result);
    37     }
    38 
    39 }

    另外,addAll(),removeAll(),retainAll()三种方法的返回值都是Boolean值,而不是集合类型,需要注意!

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  • 原文地址:https://www.cnblogs.com/shijt/p/7576304.html
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