list集合，map集合遍历

 1 import java.util.ArrayList;
 2 import java.util.Iterator;
 3 import java.util.List;
 4
 5 /**
 6 *遍历集合List
 7  * @author Men、叔
 8 *  Email [email protected]  【Men 叔 Java厂】：http://jq.qq.com/?_wv=1027&k=cfqLhZ
 9  */
10 public class Demo {
11
12     /**
13      * @param args
14      */
15     public static void main(String[] args) {
16
17         List list = new ArrayList();
18         list.add("aaa");
19        list.add("bbb");
20         //1:利用下标
21      for(int i = 0 ; i< list.size();i++){
22
23             System.out.println(list.get(i));
24        }
25         //2:for- each
26         for(Object o:list){
27           System.out.println(o);
28         }
29         //3:迭代器
30        Iterator it = list.iterator();
31        while(it.hasNext()){
32           System.out.println(it.next());
33         }
34        //4:Object数组
35       Object o[];
36         o = list.toArray();
37         for(int i =  0 ; i <o.length;i++){
38         System.out.println(o[i]);
39        }
40        //5:toString
41        System.out.println(list.toString());
42
43     }
44
45 }
46 public class Demo{
47 public static void main(String[] args) {
48
49
50   Map<String, String> map = new HashMap<String, String>();
51   map.put("1", "value1");
52   map.put("2", "value2");54
55   //1：普遍使用，二次取值
56   System.out.println("通过Map.keySet遍历key和value：");
57   for (String key : map.keySet()) {
58    System.out.println("key= "+ key + " and value= " + map.get(key));
59   }
60
61   //2:迭代器遍历
62   System.out.println("通过Map.entrySet使用iterator遍历key和value：");
63   Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
64   while (it.hasNext()) {
65    Map.Entry<String, String> entry = it.next();
66    System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
67   }
68
69   //3：foreach 推荐，尤其是容量大时
70   System.out.println("通过Map.entrySet遍历key和value");
71   for (Map.Entry<String, String> entry : map.entrySet()) {
72    System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
73   }
74
75   //4
76   System.out.println("通过Map.values()遍历所有的value，但不能遍历key");
77   for (String v : map.values()) {
78    System.out.println("value= " + v);
79   }
80  }
81 }