数组，类数组，List集合，Set集合的转化

Posted on 2017-09-01 15:00  想念熊  阅读(740)  评论(0)    收藏  举报

 

 1 import java.util.ArrayList;
 2 import java.util.Arrays;
 3 import java.util.HashSet;
 4 import java.util.List;
 5 import java.util.Set;
 6 import java.util.TreeSet;
 7 import org.junit.Test;
 8 
 9 public class Array_List_Set {
10     /**
11      * List集合转对象数组:alist.toArray();
12      */
13     @Test
14     public void ListToArray(){
15         List<Integer> alist=new ArrayList<Integer>();
16         alist.add(5);
17         alist.add(127);
18         Object[] array = alist.toArray();    
19         System.out.println(Arrays.toString(array));
20     }
21     /**
22      * Set集合转对象数组:aset.toArray();
23      */
24     @Test
25     public void SetToArray(){
26         Set<String> aset=new HashSet<String>();
27         aset.add("gr");
28         aset.add("aeh");
29         Object[] array = aset.toArray();    
30         System.out.println(Arrays.toString(array));
31     }
32     /**
33      * 对象数组转List集合:Arrays.asList(aint);
34      */
35     @Test
36     public void ArrayToList(){
37         Integer[] aint={15,64,87,36};
38         List<Integer> alist = Arrays.asList(aint);
39         System.out.println(alist.toString());
40     }
41     /**
42      * 对象数组转Set集合:先转List集合,再通过构造方法转Set集合
43      */
44     @Test
45     public void ArrayToSet(){
46         String[] astr={"fe","ag","2","wa","jt"};
47         List<String> alist = Arrays.asList(astr);
48         Set<String> aset=new HashSet<String>(alist);
49         for (String str: aset) {
50             System.out.print(str+";");
51         }
52     }
53     /**
54      * 数组和类数组的转化
55      */
56     @Test
57     public void ArrayTest(){
58         int[] aint={43,63,32,5,642};
59         Integer[] aInt = new Integer[aint.length];
60         for (int i = 0; i < aint.length; i++) {
61             aInt[i]=aint[i];
62         }
63         List<Integer> alist=Arrays.asList(aInt);
64         System.out.println(alist.toString());
65     }
66     /**
67      * 构造方法互转List和Set集合
68      */
69     @Test
70     public void ListToSet(){
71         String[] aStr={"ge","ae","4y","hx","75"};
72         List<String> alist=Arrays.asList(aStr);
73         Set<String> aset=new TreeSet<String>(alist);
74     }
75 }