Map.Entry Interface in JAVA

The Map.Entry interface enables you to work with a map entry.

The entrySet() method declared by the Map interface returns a Set containing the map entries. Each of these set elements is a Map.Entry object.

Following table shows the list of methods available in Map.Entry interface:

NOTE: A ClassCastException is thrown if v is not the correct type for the map. A NullPointerException is thrown if v is null and the map does not permit null keys. An UnsupportedOperationException is thrown if the map cannot be changed. 

Example:

package com.sample.javase.testing;

import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;

public class SortedMapInterfaceExample {

 /**
  * @param args
  */
 public static void main(String[] args) {

  SortedMap<String, String> sortedMap = new TreeMap<String, String>();
  sortedMap.put("oop1", "java");
  sortedMap.put("oop2", "c++");
  sortedMap.put("oop3", "objective-c");
  System.out.println(sortedMap);// it maintains ascending order.
  System.out.println("first key is" + sortedMap.firstKey());
  System.out.println("Last key is " + sortedMap.lastKey());

  /**
   * Following lines of code specifies hoe to get the map values form
   * iterator. For this first we need to get entry set or key set from
   * map.Here we are using entryset() method.
   */
  Set set = sortedMap.entrySet();
  for (Iterator iterator = set.iterator(); iterator.hasNext();) {

   Map.Entry entry = (Entry) iterator.next();
   System.out.println("key is " + entry.getKey());
   System.out.println("value is " + entry.getValue());
  }
  
  /**
   * Following lines of code specifies hoe to get the map values form
   * iterator. For this first we need to get entry set or key set from
   * map.Here we are using keyset() method.
   */
  Set set2 = sortedMap.keySet();
  for (Iterator iterator = set2.iterator(); iterator.hasNext();) {
   Object object = (Object) iterator.next();
   System.out.println("key is " + object + "value is " + sortedMap.get(object));
  }
 }

}