JAVA基础知识之JVM-——集合练习

Posted 2020-08-21 云中之歌

 1.创建一个Set集合，保存用户输入的数据

 

 1 package test;
 2 
 3 import java.io.BufferedReader;
 4 import java.io.IOException;
 5 import java.io.InputStreamReader;
 6 import java.util.ArrayList;
 7 import java.util.HashMap;
 8 import java.util.HashSet;
 9 import java.util.Iterator;
10 import java.util.LinkedHashSet;
11 import java.util.List;
12 import java.util.Map;
13 import java.util.Set;
14 
15 class A {
16     public int count;
17     public A(int count) {
18         this.count = count;
19     }
20     
21     public boolean equals(Object obj){
22         if (this == obj) {
23             return true;
24         }
25         if (obj != null && obj.getClass() == A.class) {
26             A r = (A)obj;
27             return r.count == this.count;
28         }
29         return false;
30     }
31     
32     public int hashCode() {
33         return this.count;
34     }
35     
36     public String toString() {
37         return this.count+"";
38     }
39     
40 }
41 public class TestCollection {
42     public static void testSet() throws Exception {
43         //Set set = new LinkedHashSet();
44         //Set set = new TreeSet();
45         Set set = new HashSet();
46         int keyIn;
47         int num = 0;
48         
49         while ( num++ < 2) {
50             //Scanner sc = new Scanner(System.in);
51             //keyIn = sc.nextInt();
52             BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
53             keyIn = Integer.parseInt(br.readLine());
54             set.add(new A(keyIn));
55         }
56         System.out.println(set);
57     }
58     
59     public static void testList() {
60         List list = new ArrayList();
61         for (int i=0; i<10; i++) {
62             list.add(new A(i));
63         }
64         System.out.println(list);
65     }
66     
67     public static void testMap() {
68         String[] str = new String[] {"a","b","a","b","c","a","b","c"};
69         Map<String, Integer> map = new HashMap();
70         Set<String> set = new LinkedHashSet();
71         for (int i = 0; i < str.length; i++) {
72             set.add(str[i]);
73         }
74         
75         
76         String key;
77         Iterator it = set.iterator();
78         while (it.hasNext()) {
79             int val = 0;
80             key = (String)it.next();
81             for (int i = 0; i < str.length; i++) {
82                 if (str[i] == key) val++;
83             }
84             map.put(key, val);
85         }
86 
87         System.out.println(map);
88     }
89     
90     public static void main(String[] args) throws Exception {
91         //TestCollection.testSet();
92         //TestCollection.testList();
93         TestCollection.testMap();
94     }
95 }