Commons Collections - MapIterator Interface

The JDK Map interface is pretty difficult to iterate as Iteration to be done on EntrySet or over the KeySet objects. MapIterator provides simple iteration over Map. Following example illustrates the same.

Example of MapIterator Interface

An example for is as follows −

import org.apache.commons.collections4.IterableMap;
import org.apache.commons.collections4.MapIterator;

public class MapIteratorTester {
   public static void main(String[] args) {
      IterableMap<String, String> map = new HashedMap<>();
      map.put("1", "One");
      map.put("2", "Two");
      map.put("3", "Three");
      map.put("4", "Four");
      map.put("5", "Five");

      MapIterator<String, String> iterator = map.mapIterator();
      while (iterator.hasNext()) {
         Object key =;
         Object value = iterator.getValue();

         System.out.println("key: " + key);
         System.out.println("Value: " + value);
         iterator.setValue(value + "_");


The output is stated below −

key: 3
Value: Three
key: 5
Value: Five
key: 2
Value: Two
key: 4
Value: Four
key: 1
Value: One
{3=Three_, 5=Five_, 2=Two_, 4=Four_, 1=One_}