Java学习---Map的学习

1. Map

1.1. map中的方法

1.2. Map.Entry

对于集合来讲，就是把kye-value的数据保存在了Map.Entry的实例之后，再在Map集合中插入了一个Map.Entry的实例化对象

Map.Entry一般用于输出集合

1.3. Map接口的常用子类

1.4. HashTable和HashMap区别

1.5. Map的标准输出(2个)

Map的方法使用集合

  1 package com.ftl;
  2 
  3 import java.util.*;
  4 
  5 
  6 class Person implements Comparable<Person>
  7 {
  8     private String name;
  9     private int age;
 10     public Person(String name, int age)
 11     {
 12         this.age = age;
 13         this.name = name;
 14     }
 15     @Override
 16     public String toString() {
 17         return "姓名：" + this.name + ", 年龄：" + this.age ;
 18     }
 19     public boolean equals(Object obj)
 20     {
 21         boolean flag = true;
 22         if ( this == obj)
 23         {
 24             return flag ;
 25         }
 26         if ( !(obj instanceof Person))
 27         {
 28             flag =  false;
 29         }
 30         Person p = (Person)obj;        
 31             if (this.name.equals(p.name)
 32                     && this.age == p.age)
 33             {
 34                 return flag;
 35             }
 36             else
 37             {
 38                 flag = false;
 39             }
 40         
 41         return flag;
 42     }
 43     
 44     public int hashCode()
 45     {
 46         return this.name.hashCode() * this.age;
 47     }
 48     
 49     @Override
 50     public int compareTo(Person per) {
 51         if ( this.age > per.age)
 52         {
 53             return 1;
 54         }
 55         else if (this.age < per.age)
 56         {
 57             return -1;
 58         }
 59         else
 60         {
 61             return this.name.compareTo(per.name);
 62         }
 63     }
 64     
 65 }
 66 
 67 
 68 public class HelloFtl {
 69     public static void main(String[] args) throws Exception {
 70         // TODO 自动生成的方法存根
 71         System.out.println("--------------------------------------");
 72             List<String> allList = null;
 73             Collection<String> col = null;
 74             allList = new ArrayList<String>();
 75             col = new ArrayList<String>();
 76             allList.add("Hello");
 77             allList.add("world");
 78             System.out.println(allList);
 79         System.out.println("--------------------------------------");
 80             col.add("HHH");
 81             col.add("FTL");
 82             col.add("WM");
 83             allList.addAll(allList.size(), col);
 84             System.out.println(allList);
 85 //        System.out.println("--------------------------------------");
 86 //            allList.remove(0);
 87 //            System.out.println(allList);
 88 //        System.out.println("--------------------------------------");
 89             allList.removeAll(col);
 90 //            System.out.println(allList);
 91         System.out.println("--------------------------------------");
 92             for(int i = 0; i < allList.size(); i++)
 93             {
 94                 System.out.print(allList.get(i) + "、");
 95             }
 96         System.out.println();
 97         System.out.println("--------------------------------------");
 98             for(int i = allList.size()-1; i >=0 ; i--)
 99             {
100                 System.out.print(allList.get(i) + "、");
101             }
102             System.out.println();
103         System.out.println("--------------------------------------");
104             Object[] obj = allList.toArray();
105             for(int i = 0; i <obj.length; i++)
106             {
107                 String temp = (String)obj[i];
108                 System.out.print(temp + "、");
109             }
110         System.out.println();
111         System.out.println("--------------------------------------");
112         System.out.println(allList.contains("HHH") ? "lv存在": "lv不存在");
113         System.out.println(allList.contains("lv的位置是：" + allList.indexOf("HHH")));
114         System.out.println(allList.contains("allList否为空" + allList.isEmpty() ));
115         System.out.println("--------------------------------------");
116         LinkedList<String> link = new LinkedList<String>();
117         link.add("A");
118         link.add("B");
119         link.add("C");
120         link.addFirst("Root");
121         link.addLast("End");
122         System.out.print(link);
123         System.out.println();
124         System.out.println("Element: " + link.element());
125         System.out.println("Pool: " + link.poll());
126         System.out.print(link);
127         System.out.println();
128         System.out.println("Peek: " + link.peek());
129         System.out.print(link);
130         System.out.println();
131         System.out.println("--------------------------------------");
132         for ( int i = 0; i < link.size(); i++)
133             {
134                 System.out.print("Pool: "
135                         + "" + link.poll() + "、");
136             }
137         System.out.println();
138         System.out.println("--------------------------------------");
139         Set<Person > set = new HashSet<Person>();
140 //        Set<Person> set = new TreeSet<Person>();
141         set.add(new Person("Root2", 12));
142         set.add(new Person("AA", 21));
143         set.add(new Person("BB", 22));
144         set.add(new Person("CC", 22));
145         set.add(new Person("CC", 22));
146         set.add(new Person("CC", 12));
147         System.out.println( set);
148         System.out.println("--------------------------------------");
149         System.out.println("Iterator: ");
150         Iterator<Person> iter = set.iterator();
151         while(iter.hasNext())
152         {
153             System.out.print(iter.next() + "、");
154         }
155         System.out.println();
156         System.out.println("--------------------------------------");
157         while(iter.hasNext())
158         {
159             Person str = iter.next();
160             if ("CC".equals(str))
161             {
162                 iter.remove();
163             }
164             else
165             {
166                 System.out.print(str + "、");
167             }
168         }
169         System.out.println("--------------------------------------");
170         Map<String ,String> map = null;
171         map = new HashMap<String, String>();
172         map.put("04122", "FTL1012");
173         map.put("04122076", "FTL");
174         map.put("04122078", "1012");
175         System.out.println(map.containsKey("04122"));
176         System.out.println(map.containsValue("04122"));
177         System.out.println("04122 --> " + map.get("04122"));
178         System.out.println("--------------------------------------");
179         System.out.println("HashMap 中所有的Key:");
180         Set<String> sset = map.keySet();
181         Iterator<String> it = sset.iterator();
182         while (it.hasNext())
183         {
184             String t = (String) it.next();
185             System.out.print( t + "\t");
186         }
187         System.out.println("--------------------------------------");
188         System.out.println("HashMap 中所有的Value:");
189         Collection<String> co = map.values();
190         Iterator<String> itt = co.iterator();
191         while (itt.hasNext())
192         {
193             String tt = (String) itt.next();
194             System.out.print( tt + "\t");
195         }
196         System.out.println("--------------------------------------");
197         map = new TreeMap<String, String>();
198         map.put("04122", "FTL1012");
199         map.put("04122076", "FTL");
200         map.put("04122078", "1012");
201         Set<String> keys = map.keySet();
202         Iterator<String> key = keys.iterator();
203         System.out.println("TreeMap 中所有的Key:");
204         while (key.hasNext())
205         {
206             String tt =   (String)key.next();
207             System.out.print( key + "\t");
208         }
209         System.out.println("--------------------------------------");
210         Collection<String> ccc = map.values();
211         Iterator<String> ttt = ccc.iterator();
212         System.out.println("TreeMap 中所有的Value:");
213         while (ttt.hasNext())
214         {
215             String tt =  (String) ttt.next();
216             System.out.print( ttt + "\t");
217         }
218         
219         
220         System.out.println("--------------------------------------");
221     }
222 };

View Code

Map的标准输出示例：

 1 package com.ftl; 
 2 import java.util.Collection; 
 3 import java.util.Iterator; 
 4 import java.util.Map; 
 5 import java.util.Map.Entry; 
 6 import java.util.Set; 
 7 import java.util.TreeMap; 
 8 public class HelloFtl { 
 9 public static void main(String[] args){
10     Map<String,String>map = new TreeMap<>(); 
11     map.put("Hello", "world"); 
12     map.put("Hello1", "world1"); 
13     map.put("Hello2", "world2"); 
14     map.put("Hello3", "world3"); 
15     String str = map.get("Hello"); 
16     Set<String> set = map.keySet(); 
17     Collection<String> values = map.values(); 
18     Iterator<String> iterator = set.iterator(); 
19     Iterator<String> iter = values.iterator(); 
20     System.out.println("------------------------------------");
21     System.out.println("\nforeach方法："); 
22     for (String s : values) { 
23     System.out.print(s+"、"); 
24     } 
25     System.out.println("------------------------------------");
26     System.out.println("\nIterator方法："); 
27     while(iterator.hasNext()){ 
28     System.out.print(iterator.next()+"、"); 
29     } 
30     System.out.println("------------------------------------");
31     System.out.println("\nMap的标准输出_1(Map.entrySet)："); 
32     Set<Entry<String,String>> entrySet = map.entrySet(); 
33     Iterator<Map.Entry<String, String>> it = entrySet.iterator(); 
34     while(it.hasNext()){ 
35     Map.Entry<String, String> next = it.next(); 
36     System.out.print(next.getKey()+"-->: "+next.getValue()+"\n"); 
37     } 
38     System.out.println("------------------------------------");
39     System.out.println("\nMap的标准输出_2(Foreach)："); 
40     for (Map.Entry<String, String> entry : entrySet) { 
41     System.out.print(entry.getKey()+"-->: "+entry.getValue()+"\n"); 
42     } 
43     System.out.println("------------------------------------");
44     System.out.println("Map.entrySet()大小："+map.entrySet().size()); 
45     System.out.println("------------------------------------");
46 }}

View Code

Map的迭代输出

 1 package test;
 2 import java.util.Collection;
 3 import java.util.HashMap;
 4 import java.util.Iterator;
 5 import java.util.Map;
 6 import java.util.Set;
 7 public class Test
 8 {
 9     public static void main(String[] args) throws Exception
10     {
11         Map<String,String> map = new HashMap();
12         map.put("hello", "world");
13         map.put("hello1", "world1");
14         map.put("hello2", "world2");
15         map.put("hello3", "world3");
16         map.put("hello4", "world4");
17         String str = map.get("hello");
18         boolean containsKey = map.containsKey("hello");
19         boolean containsValue = map.containsValue("world");
20         Set<String> keySet = map.keySet();
21         Collection<String> values = map.values();
22 
23         Iterator<String> iter = values.iterator();
24         while(iter.hasNext()){
25             String s = iter.next();
26             System.out.println(s+"E");
27         }
28         
29     }
30 }

View Code

posted @ 2018-07-18 07:48 小a玖拾柒阅读(348) 评论(0) 编辑收藏举报

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