JAVA

does key repeats in hashmap

HashMap does not allow duplicate keys however it allows to have duplicate values. HashSet permits to have a single null value. HashMap permits single null key and any number of null values.

No Duplicate Key on HashMap

import java.util.*;  
public class hashmapeg2{  
 public static void main(String args[]){  
   HashMap<Integer,String> map=new HashMap<Integer,String>();//Creating HashMap    
   map.put(1,"Cat");  //Put elements in Map  
   map.put(2,"Dog");    
   map.put(3,"Markhor");   
   map.put(4,"Peacock");   
   map.put(1,"Leopard");
       
   System.out.println("Iterating Hashmap...");  
   for(Map.Entry m : map.entrySet()){    
    System.out.println(m.getKey()+" "+m.getValue());    
   }  
}  
}