The traversal of the Java base map

There are four ways to traverse the map collection:

public static void Main (string[] args) {map<string, string> Map = new hashmap<string, string> ();  Map.put ("1", "value1");  Map.put ("2", "value2");    Map.put ("3", "Value3"); The first type:universally used, two times valueSystem.out.println ("Traverse key and value by Map.keyset");  For (String Key:map.keySet ()) {System.out.println ("key=" + key + "and value=" + map.get (key)); }//The second type of SYSTEM.OUT.PRINTLN ("using iterator to traverse key and value through Map.entryset：");  Iterator<map.entry<string, string>> it = Map.entryset (). Iterator ();   while (It.hasnext ()) {map.entry<string, string> Entry = It.next ();  System.out.println ("key=" + entry.getkey () + "and value=" + entry.getvalue ()); }//Third type: recommended, especiallyLarge CapacityWhen System.out.println ("traversing key and value via Map.entryset"); For (map.entry<string, string> entry:map.entrySet ()) {System.out.println ("key=" + entry.getkey () + "and value  = "+ Entry.getvalue ()); }//Fourth type SYSTEM.OUT.PRINTLN ("traverse all value through Map.values (), but cannot traverse key");  For (String v:map.values ()) {System.out.println ("value=" + V); } }

　　

The traversal of the Java base map