JAVA-Map Two traversal

 1 package Demo01;
 2 
 3 import java.util.HashMap;
 4 import java.util.Map;
 5 import java.util.Set;
 6 
 7 public class test01 {
 8     public static void main(String[] args) {
 9         Map<String,String> a = new HashMap<String, String>();
10         a.put("a", "1");
11         a.put("b", "12");
12         a.put("c", "13");
13         a.put("a", "12");
 14          System.out.println (A);
 15          // way: Get all the keys, then the value obtained according to the key
 16          // Get all map key, all keys stored in a set Set, traversal set the set value to get the value of the get method using the Map 
. 17          set <String> Keys = a.keySet ();
 18 is          for (String Key: Keys) {
 . 19              System.out.println (Key + ":" + a.get (Key));
 20 is          }
 21 is          @ way: direct access to all key-value pairs
 22          // interface represents a key-value pair is the Entry
 23 is          // all keys stored in the Map set set to
 24          // set storing a set of key-value pairs is
 25          // external classes. class inner 
26         Set<Map.Entry<String,String>> entrys=a.entrySet();
27         for (Map.Entry<String, String> entry : entrys) {
28             System.out.println(entry.getKey()+":"+entry.getValue());
29         }
30     }
31       
32         
33         
34         
35         
36         
37         
38         
39         
40     
41 }