Java TreeMap containsKey() Method Last Updated : 16 May, 2025 Comments Improve Suggest changes Like Article Like Report The containsKey() method in Java is used to check if a given key exists in a TreeMap. If the key is present in the map, it returns true, otherwise, it returns false. This method is very helpful when we need to verify whether a mapping exists before performing any operation on it.Syntax of TreeMap containsKey() MethodtreeMap.containsKey(key);Parameter: key: This is the key whose mapping is supposed to be checked inside a map.Return Value: The method returns boolean true if the presence of the key is detected else false.Examples of the TreeMap containsKey() Method in JavaExample 1: In this example, we are going to use a TreeMap with Integer keys and String values. We will check the presence of keys using the containsKey() method. Java // Java program to demonstrate // TreeMap containsKey() method import java.util.TreeMap; public class Geeks { public static void main(String[] args) { // Create a TreeMap with Integer keys TreeMap<Integer, String> tm = new TreeMap<>(); // Add key-value pairs tm.put(10, "Geeks"); tm.put(15, "4"); tm.put(20, "Geeks"); tm.put(25, "Welcomes"); tm.put(30, "You"); System.out.println("Initial Mappings are: " + tm); // Check if key 20 is present System.out.println("Is the key '20' present? " + tm.containsKey(20)); // Check if key 5 is present System.out.println("Is the key '5' present? " + tm.containsKey(5)); } } OutputInitial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You} Is the key '20' present? true Is the key '5' present? false Example 2: In this example, we are going to create a TreeMap with String keys and Integer values. Here, we will check for the existence of some string keys. Java // Java program to demonstrate // TreeMap containsKey() method import java.util.TreeMap; public class Geeks { public static void main(String[] args) { // Create a TreeMap with String keys TreeMap<String, Integer> tm = new TreeMap<>(); // Add key-value pairs tm.put("Geeks", 10); tm.put("4", 15); tm.put("Geeks", 20); tm.put("Welcomes", 25); tm.put("You", 30); System.out.println("Initial Mappings are: " + tm); // Check if key is present System.out.println("Is the key 'Welcomes' present? " + tm.containsKey("Welcomes")); System.out.println("Is the key 'World' present? " + tm.containsKey("World")); } } OutputInitial Mappings are: {4=15, Geeks=20, Welcomes=25, You=30} Is the key 'Welcomes' present? true Is the key 'World' present? false Important Points:This method checks whether a particular key present or not in the map.This method works with all types of keys that is Integer, String, etc.This method is very useful for avoiding NullPointerExceptions or for validating keys before updates.If there are duplicate keys are added, the latest value will overwrite the old one, but the key will still be present. Comment More infoAdvertise with us Next Article TreeMap containsValue() Method in Java With Examples chinmoy lenka Follow Improve Article Tags : Java Java-Collections Java - util package java-TreeMap Practice Tags : JavaJava-Collections Similar Reads TreeMap in Java TreeMap is a part of the Java Collection Framework. It implements the Map and NavigableMap interface and extends the AbstractMap class. 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