java.util.TreeMap.containsKey() Method


The containsKey(Object key) method is used to return 'true' if this map contains a mapping for the specified key.


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

public boolean containsKey(Object key)


key − This is the key whose presence in this map is to be tested.

Return Value

The method call returns true if this map contains a mapping for the specified key.


  • ClassCastException − This is thrown if the specified key cannot be compared with the keys currently in the map.

  • NullPointerException − This is thrown if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys.


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

package com.tutorialspoint;

import java.util.*;

public class TreeMapDemo {
   public static void main(String[] args) {
      // creating tree map 
      NavigableMap<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");

      System.out.println("Checking key value 6");
      System.out.println("Value for key 6 exists: "+ treemap.containsKey(6));

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

Checking key value 6
Value for key 6 exists: true
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