判断Map集合中是否存在某一个key

 1 方法一：
 2 Map<String,String> hashmp = ne HashMap();
 3 hashmp.put("aa", "111");
 4 hashmap.containsKey("xxx");
 5 
 6 
 7 方法二：keySet()
 8 HashMap hashmp = ne HashMap();
 9 hashmp.put("aa", "111");
10 Set set = hashmp.keySet();
11 Iterator iter = set.iterator();
12 while (iter.hasNext()) {
13 String key = (String) iter.next();
14 // printkey
15 }
16 // traverse
17 for (String key : list.get(pos).keySet() ) {
18 myKey = key;
19 }
20 
21 
22 方法三：entrySet()
23 HashMap map;
24 Iterator i = map.entrySet().iterator();
25 while (i.hasNext()) {
26 Object obj = i.next();
27 String key = obj.toString();
28 }
29 // or
30 while (i.hasNext()) {
31 Entry entry = (java.util.Map.Entry)it.next();
32 entry.getkey();
33 entry.getValue();
34 }