How to loop HashMap in java?

   
Consider the following values in HashMap are as below:


1).heera babu
2).value1
3).value2
4).techieuncle.com

Let's understand some basic concepts, in the below program code, you will see
         Iterator   itr = hm.keySet().iterator();
Here, the code in below program says that we are generating set of keys using keyset() method and then calling iterator() method in this set of keys.
Now, we can use while loop and then display all data based on key traversal.

        while(itr.hasNext())
  {
   System.out.println(hm.get(itr.next())); 
  }

Another way to understand the iterate the data.
Set  myset  =hm.keySet();
System.out.println("Set of Keys are: "+myset);

This code line will display data as below:
Set of Keys are: [null, 1, 2, 100]

Continue code:
Iterator itr =myset.iterator();
         while(itr.hasNext())
         {
              System.out.println(hm.get(itr.next()));
         }


 

   
Now the complete code is as below:
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;

public class TestMap
{
    public static void main(String a[])
    {
         HashMap hm = new HashMap();
         hm.put(1, "value1");
         hm.put(2, "value2");
         hm.put(null, "heera");
         hm.put(null, "heera babu");
         hm.put(100, "techieuncle.com");

         Iterator   itr = hm.keySet().iterator();
         while(itr.hasNext())
         {
              System.out.println(hm.get(itr.next()));
         }
    }
}


 

Console Output:
heera babu
value1
value2
techieuncle.com