Java如何遍历Map的所有的元素

JDK1.4中

[java] view plain copy print ?

1. <font color="#0000ff">Map map = new HashMap();
2.  
3.     Iterator it = map.entrySet().iterator(); 
4.  
5.     while (it.hasNext()) { 
6.  
7.         Map.Entry entry = (Map.Entry) it.next(); 
8.  
9.         Object key = entry.getKey(); 
10.  
11.         Object value = entry.getValue(); 
12.  
13. }</font> 

Map map = new HashMap();

    Iterator it = map.entrySet().iterator();

    while (it.hasNext()) {

        Map.Entry entry = (Map.Entry) it.next();

        Object key = entry.getKey();

        Object value = entry.getValue();

}

JDK1.5中,应用新特性For-Each循环

[java] view plain copy print ?

1. Map m = new HashMap(); 
2.  
3. for(Object o : map.keySet()){ 
4.  
5.     map.get(o); 
6.  
7. } 

Map m = new HashMap();

for(Object o : map.keySet()){

    map.get(o);

}

返回的 set 中的每个元素都是一个 Map.Entry 类型。

[java] view plain copy print ?

1. <font color="#0000ff">private Hashtable<String, String> emails = new Hashtable<String, String>();</font> 

private Hashtable<String, String> emails = new Hashtable<String, String>();

  另外 我们可以先把hashMap 转为集合Collection，再迭代输出，不过得到的对象

[java] view plain copy print ?

1. <font color="#0000ff">//方法一: 用entrySet() 
2.  
3.    Iterator it = emails.entrySet().iterator(); 
4.  
5.    while(it.hasNext()){ 
6.  
7.     Map.Entry m=(Map.Entry)it.next(); 
8.  
9.     logger.info("email-" + m.getKey() + ":" + m.getValue()); 
10.  
11.    } 
12.  
13.    
14.  
15.    // 方法二：jdk1.5支持，用entrySet()和For-Each循环() 
16.  
17.    for (Map.Entry<String, String> m : emails.entrySet()) { 
18.  
19.     
20.  
21.     logger.info("email-" + m.getKey() + ":" + m.getValue()); 
22.  
23.    } 
24.  
25.    
26.  
27.    // 方法三：用keySet() 
28.  
29.    Iterator it = emails.keySet().iterator(); 
30.  
31.    while (it.hasNext()){ 
32.  
33.     String key; 
34.  
35.     key=(String)it.next(); 
36.  
37.     logger.info("email-" + key + ":" + emails.get(key)); 
38.  
39.    } 
40.  
41.  
42.  
43. // 方法五：jdk1.5支持，用keySEt()和For-Each循环 
44.  
45.  
46.  
47. for(Object m: emails.keySet()){ 
48.  
49.     logger.info("email-" + m+ ":" + emails.get(m)); 
50.  
51.    } 
52. </font> 

 //方法一: 用entrySet()

   Iterator it = emails.entrySet().iterator();

   while(it.hasNext()){

    Map.Entry m=(Map.Entry)it.next();

    logger.info("email-" + m.getKey() + ":" + m.getValue());

   }

  

   // 方法二：jdk1.5支持，用entrySet()和For-Each循环()

   for (Map.Entry<String, String> m : emails.entrySet()) {

   

    logger.info("email-" + m.getKey() + ":" + m.getValue());

   }

  

   // 方法三：用keySet()

   Iterator it = emails.keySet().iterator();

   while (it.hasNext()){

    String key;

    key=(String)it.next();

    logger.info("email-" + key + ":" + emails.get(key));

   }



// 方法五：jdk1.5支持，用keySEt()和For-Each循环



for(Object m: emails.keySet()){

    logger.info("email-" + m+ ":" + emails.get(m));

   }

      Map    aa    =    new    HashMap();       aa.put("tmp1",    new    Object());      //追加      替换用同样的函数.       aa.remove("temp1");                        //删除       for    (Iterator    i    =    aa.values().iterator();    i.hasNext();    )    {               Object    temp    =    i.next();       }          //遍历  

  

来个完整的，包含TreeSet的元素内部排序的

[java] view plaincopyprint?

1. public static void main(String[] args) { 
2.  
3.    ArrayList<String> list = new ArrayList<String>(); 
4.  
5.    HashMap<Object,Object> hash = new HashMap<Object,Object>(); 
6.  
7.    TreeMap<Object,Object> treeMap = new TreeMap<Object,Object>(); 
8.  
9.    list.add("a"); 
10.  
11.    list.add("b"); 
12.  
13.    list.add("c"); 
14.  
15.    
16.  
17.    hash.put(3, 3); 
18.  
19.    hash.put(4, 4); 
20.  
21.    hash.put(5, 5); 
22.  
23.    hash.put(6, 6); 
24.  
25.    hash.put(1, 1); 
26.  
27.    hash.put(2, 2); 
28.  
29.    
30.  
31.    treeMap.put(1, 1); 
32.  
33.    treeMap.put(2, 2); 
34.  
35.    treeMap.put(3, 3); 
36.  
37.    treeMap.put(4, 4); 
38.  
39.    treeMap.put(5, 5); 
40.  
41.    treeMap.put(6, 6); 
42.  
43.    
44.  
45.    //list遍历 
46.  
47.    for(String m: list){ 
48.  
49.     System.out.println(m); 
50.  
51.    } 
52.  
53.    // hashmap entrySet() 遍历 
54.  
55.    for(Map.Entry<Object,Object> m: hash.entrySet()){ 
56.  
57.     System.out.println(m.getKey()+"---"+m.getValue()); 
58.  
59.    } 
60.  
61.    //hashmap keySet() 遍历 
62.  
63.    for(Object m: hash.keySet()){ 
64.  
65.     System.out.println(m+"---"+hash.get(m)); 
66.  
67.    } 
68.  
69.    // treemap keySet()遍历 
70.  
71.    for(Object m: treeMap.keySet()){ 
72.  
73.     System.out.println(m+"---"+treeMap.get(m)); 
74.  
75.    } 
76.  
77. } 

 

 

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