课堂所讲整理：Set和Map

Posted 2020-06-21 柒寒

Set相关知识：

 1 package org.hanqi.array;
 2 
 3 import java.util.*;
 4 
 5 public class Test2 {
 6 
 7     public static void main(String[] args) {
 8         
 9 //        int i;//默认i=0
10 //        int [] m = new int[5];//赋值了5个0
11         
12         //哈希
13         Set<String> s = new HashSet<String>();
14         HashSet<String> s1 = new HashSet<String>();
15         
16         if(s.add("a"))
17         {
18             System.out.println("保存a成功");
19         }        
20         s.add("b");
21         s.add("c");
22         s.add("d");
23         s.add("e");
24         s.add("f");
25         s.add("g");
26         
27         if(!s.add("a"))
28         {
29             System.out.println("保存a失败");
30         }
31         //s.add("a");
32         //s.add("a");
33         
34         for(String t:s)
35         {
36             System.out.print(t);
37         }
38         
39         System.out.println();
40         
41         System.out.println("s的size="+s.size());
42 
43         if(s.remove("d"))
44         {
45             System.out.println("移除成功");
46         }
47         else
48         {
49             System.out.println("移除失败");
50         }
51         
52         System.out.println("s的size="+s.size());
53         
54         //迭代器
55         Iterator<String> it = s.iterator();
56         while(it.hasNext())
57         {
58             String t = it.next();
59             if(t.equals("c"))
60             {
61                 it.remove();
62             }
63             else
64             {
65                 System.out.print(t);
66             }
67             
68         }
69         
70         System.out.println();
71         
72         System.out.println("s的size="+s.size());
73         
74         System.out.println("TreeSet");
75         
76         Set<String> s2 = new TreeSet<String>();        
77         
78         s2.add("f");
79         s2.add("b");
80         s2.add("d");
81         s2.add("c");
82         s2.add("e");
83         s2.add("a");
84         s2.add("g");
85                         
86         for(String t:s2)
87         {
88             System.out.print(t);
89         }
90         
91         System.out.println();
92         
93         System.out.println("s2的size="+s2.size());
94     }
95 }

运行结果为：

Map相关知识：

 1 package org.hanqi.array;
 2 
 3 import java.util.*;
 4 
 5 public class Test3 {
 6 
 7     public static void main(String[] args) {
 8         
 9         Map<String,String> m = new HashMap<String,String>();
10         
11         m.put("7", "淄博");
12         m.put("9", "济南");
13         m.put("5", "青岛");
14         m.put("1", "青岛");
15         m.put("8", "青岛");
16         m.put("6", "青岛");
17         m.put("3", "青岛");
18         m.put("2", "青岛");
19         m.put("0", "青岛");        
20         //长度
21         System.out.println("长度="+m.size());
22         m.put("0534", "青岛");
23         m.put(null, null);
24         System.out.println("长度="+m.size());
25         //根据key获取value
26         System.out.println("0533="+m.get("0533"));
27         //key是否存在
28         if(m.containsKey("0533"))
29         {
30             System.out.println("key 0533已存在");
31         }
32         //value是否存在
33         if(m.containsValue("淄博"))
34         {
35             System.out.println("value 淄博已存在");
36         }
37         //遍历
38         for(String k:m.keySet())
39         {
40             System.out.println(k+"="+m.get(k));
41         }
42     }
43 }

运行结果为：

相关思维导图：