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Java TreeMap containsKey() Method with Example

TreeMap Class containsKey() method: Here, we are going to learn about the containsKey() method of TreeMap Class with its syntax and example.
Submitted by Preeti Jain, on February 19, 2020

TreeMap Class containsKey() method

  • containsKey() method is available in java.util package.
  • containsKey() method is used to check whether this TreeMap contains a value element for the given key element or not.
  • containsKey() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
  • containsKey() method may throw an exception at the time of checking association for the given key element.
    • ClassCastException: This exception may throw when the given parameter is incompatible to compare.
    • NullPointerException: This exception may throw when the given parameter is null exists.


    public boolean containsKey(Object key_ele);


  • Object key_ele – represents the key element whose existence is to be checked in this TreeMap.

Return value:

The return type of the method is boolean, it returns true when this TreeMap holds mappings for the given key element (key_ele) otherwise it returns false.


// Java program to demonstrate the example 
// of boolean containsKey(Object key_ele) 
// method of TreeMap

import java.util.*;

public class ContainsKeyOfTreeMap {
    public static void main(String[] args) {
        // Instantiates a TreeMap object
        NavigableMap < Integer, String > tree_map = new TreeMap < Integer, String > ();

        // By using put() method is to add
        // key-value pairs in a TreeMap
        tree_map.put(10, "C");
        tree_map.put(20, "C++");
        tree_map.put(50, "JAVA");
        tree_map.put(40, "PHP");
        tree_map.put(30, "SFDC");

        // Display TreeMap 
        System.out.println("TreeMap: " + tree_map);

        // By using containsKey() method is to 
        // check whether the given key element
        // exists or not exists in this TreeMap
        boolean status = tree_map.containsKey(50);

        // Display Status
        System.out.println("tree_map.containsKey(50): " + status);


TreeMap: {10=C, 20=C++, 30=SFDC, 40=PHP, 50=JAVA}
tree_map.containsKey(50): true


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