Map.Entry Interface in Java

Map.Entry interface helps us iterating a Map class such as HashMap, TreeMap etc. In this tutorial, we will learn methods and usage of Map.Entry interface in Java.

Method of Map.Entry interface

1) boolean equals(Object o): Compares the specified object with this entry for equality.
2) Key getKey(): Returns the key corresponding to this entry.
3) Value getValue(): Returns the value corresponding to this entry.
4) int hashCode(): Returns the hash code value for this map entry.
5) Value setValue(V value): Replaces the value corresponding to this entry with the specified value (optional operation).

Example and Usage of Map.Entry

In this example, we have a Map collection class TreeMap and we are iterating and displaying its key & value pairs using Map.Entry interfaces. Here we have used getKey() and getValue() methods of Map.Entry interface in order to get the key & value pairs.

import java.util.*;
class TreeMapExample {
  public static void main(String args[]) {
     // Creating TreeMap object
     TreeMap<String, Integer> tm = new TreeMap<String, Integer>();
     // Adding elements to the Map
     tm.put("Chaitanya", 27);
     tm.put("Raghu", 35);
     tm.put("Rajeev", 37);
     tm.put("Syed", 28);
     tm.put("Hugo", 32);
 
     // Getting a set of the entries
     Set set = tm.entrySet();
     // Get an iterator
     Iterator it = set.iterator();
     // Display elements
     while(it.hasNext()) {
        Map.Entry me = (Map.Entry)it.next();
        System.out.print("Key: "+me.getKey() + " & Value: ");
        System.out.println(me.getValue());
     }
  }
}

Output:

Key: Chaitanya & Value: 27
Key: Hugo & Value: 32
Key: Raghu & Value: 35
Key: Rajeev & Value: 37
Key: Syed & Value: 28

Reference:

Map.Entry javadoc