hashmap用法笔记
View Code
1 package com.app;
2
3 import java.util.HashMap;
4 import java.util.Iterator;
5
6 public class app {
7
8 /**
9 * @param args
10 */
11 public static void main(String[] args) {
12 // TODO Auto-generated method stub
13 HashMap<String, Double> map = new HashMap<String, Double> ();
14
15 map.put("hello", 1.0);
16 map.put("fine", 2.0);
17 map.put("suck", 3.0);
18
19 Iterator<String> it = map.keySet().iterator();
20
21 if(map.containsKey("why")){
22 System.out.println("Key why exist");
23 }
24
25 if(map.containsValue(2.0)){
26 System.out.println("Value 2 exist");
27 }
28
29 /***Hash的遍历***/
30 if(!map.isEmpty()){
31 while(it.hasNext()){
32 String tempKey = it.next();
33 if(tempKey.equals("fine")){
34 Double tempValue = map.get(tempKey) + 10;
35 map.put(tempKey, tempValue);
36
37 System.out.println("fine is update to " + tempValue);
38 }else{
39 System.out.println(map.get(tempKey));
40 }
41 }
42 }else{
43 System.out.println("map is empty");
44 }
45
46 map.clear();
47
48 if(map.isEmpty()){
49 System.out.println("map is empty");
50 }
51 }
52 }
hashmap的排序：
View Code
1 package com.app;
2
3 import java.util.ArrayList;
4 import java.util.Collections;
5 import java.util.Comparator;
6 import java.util.HashMap;
7 import java.util.List;
8 import java.util.Map;
9
10 public class app {
11
12 /**
13 * @param args
14 */
15 public static void main(String[] args) {
16 // TODO Auto-generated method stub
17 Map<String, Integer> map = new HashMap<String, Integer>();
18 map.put("hello", 1);
19 map.put("fine", 3);
20 map.put("abandon", 2);
21
22 List<Map.Entry<String, Integer>> list =
23 new ArrayList<Map.Entry<String, Integer>>(map.entrySet());
24
25 for(int i = 0; i < list.size(); i++){
26 String id = list.get(i).getKey();
27 System.out.println(id);
28 }
29
30 Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() {
31 public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2){
32 return (o1.getKey()).toString().compareTo(o2.getKey());
33 }//String类的compareTo方法实现字典排序
34 });
35
36 for(int i = 0; i < list.size(); i++){
37 String id = list.get(i).getKey();
38 System.out.println(id);
39 }
40 }
41 }