java.util.TreeMap.keySet() Method

Description

ThekeySet() method is used to return a Set view of the keys contained in this map. The set's iterator returns the keys in ascending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa.

Declaration

Following is the declaration for java.util.TreeMap.keySet() method.

public Set<K> keySet()

Parameters

• NA

Return Value

The method call returns a set view of the keys contained in this map.

Exception

• NA

Example

The following example shows the usage of java.util.TreeMap.keySet() method.

package com.tutorialspoint;

import java.util.*;

public class TreeMapDemo {
   public static void main(String[] args) {
      // creating tree map 
      TreeMap<Integer, String> treemap = new TreeMap<Integer, String>();
      
      // populating tree map
      treemap.put(2, "two");
      treemap.put(1, "one");
      treemap.put(3, "three");
      treemap.put(6, "six");
      treemap.put(5, "five");
      
      // creating set
      Set set=treemap.keySet();
      
      // getting set view         
      System.out.println("Checking values of the set");
      System.out.println("Value is: "+set);
   }    
}

Let us compile and run the above program, this will produce the following result.

Checking values of the set
Value is: [1, 2, 3, 5, 6]