Java deletes elements when traversing map

 package net.nie.test;
Import Java.util.HashMap;
Import Java.util.Iterator;

Import Java.util.Map;
    
   public class Hashmaptest {private static Map<integer, string> map=new hashmap<integer,string> ();   /** 1.HashMap class mappings are not guaranteed in order; Some mappings can explicitly guarantee their order: TREEMAP class * 2. In traversing the map, you cannot modify and delete elements with Map.put (Key,newval), Map.Remove (key).  
    A concurrent modification exception can be raised by removing the current iteration element * from the collection pointed to by the iterator by removing (): * To remove the element from the access.
        * */public static void main (string[] args) {map.put (1, "one");
        Map.put (2, "two");
        Map.put (3, "three");
        Map.put (4, "four");
        Map.put (5, "five");
        Map.put (6, "six");
        Map.put (7, "seven");
        Map.put (8, "eight");
        Map.put (5, "five");
        Map.put (9, "nine");
        Map.put ("ten");
        Iterator<map.entry<integer, string>> it = Map.entryset (). iterator ();
     while (It.hasnext ()) {Map.entry<integer, string> entry=it.next ();       int Key=entry.getkey ();
                if (key%2==1) {System.out.println ("delete this:" +key+ "=" +key);   Map.put (Key, "odd");      Concurrentmodificationexception//map.remove (key);        Concurrentmodificationexception It.remove ();
        OK}//traverse the current map; This new for loop cannot modify the content of the map because it does not pass through iterators.
        System.out.println ("-------NT final Map element traversal:");
            For (Map.entry<integer, string> entry:map.entrySet ()) {int K=entry.getkey ();
            String V=entry.getvalue ();
        System.out.println (k + "=" +v); }
    }
}