How to get all keys in Java TreeMap?

This Java Example shows how to retrieve all keys contained in TreeMap using keySet method of Java TreeMap class.

import java.util.Set;
import java.util.TreeMap;

public class GetKeysFromTreeMapExample {

 public static void main(String[] args) {

  // create object of TreeMap

  TreeMap phoneBook = new TreeMap();

  // Adding key value pairs to TreeMap

  phoneBook.put("John", "245745");
  phoneBook.put("Joy", "245786");
  phoneBook.put("Roy", "233783");

  /**
   * Set keySet() - Returns a set view of the keys
   * contained in this map in ascending order.
   **/

  Set nameSet = phoneBook.keySet();

  System.out.println("Names in the phone book are :");

  for (Object name : nameSet) {
   System.out.println("Name: " + name);
  }

 }
}

The output is:


Names in the phone book are :
Name: John
Name: Joy
Name: Roy