The java.util.LinkedHashMap.containsKey() method is used to check whether a particular key is being mapped into the LinkedHashMap or not. It takes the key element as a parameter and returns True if that element is mapped in the map.
Syntax:
Linked_Hash_Map.containsKey(key_element)
Parameters: The method takes just one parameter key_element that refers to the key whose mapping is supposed to be checked inside a map.
Return Type: The method returns boolean true if the presence of the key is detected else false.
Example 1: Mapping String Values to Integer Keys.
Java
// Java code to illustrate the containsKey() methodimport java.util.*; public class Linked_Hash_Map_Demo { public static void main(String[] args) { // Creating an empty LinkedHashMap LinkedHashMap<Integer, String> li_hash_map = new LinkedHashMap<Integer, String>(); // Mapping string values to int keys li_hash_map.put(10, "Geeks"); li_hash_map.put(15, "4"); li_hash_map.put(20, "Geeks"); li_hash_map.put(25, "Welcomes"); li_hash_map.put(30, "You"); // Displaying the LinkedHashMap System.out.println("Initial Mappings are: " + li_hash_map); // Checking for the key_element '20' System.out.println("Is the key '20' present? " + li_hash_map.containsKey(20)); // Checking for the key_element '5' System.out.println("Is the key '5' present? " + li_hash_map.containsKey(5)); }} |
Output:
Initial 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: Mapping Integer Values to String Keys.
Java
// Java code to illustrate the containsKey() methodimport java.util.*; public class Hash_Map_Demo { public static void main(String[] args) { // Creating an empty LinkedHashMap LinkedHashMap<String, Integer> li_hash_map = new LinkedHashMap<String, Integer>(); // Mapping int values to string keys li_hash_map.put("Geeks", 10); li_hash_map.put("4", 15); li_hash_map.put("Geeks", 20); li_hash_map.put("Welcomes", 25); li_hash_map.put("You", 30); // Displaying the LinkedHashMapHashMap System.out.println("Initial Mappings are: " + li_hash_map); // Checking for the key_element 'Welcomes' System.out.println("Is the key 'Welcomes' present? " + li_hash_map.containsKey("Welcomes")); // Checking for the key_element 'World' System.out.println("Is the key 'World' present? " + li_hash_map.containsKey("World")); }} |
Output:
Initial Mappings are: {Geeks=20, 4=15, Welcomes=25, You=30}
Is the key 'Welcomes' present? true
Is the key 'World' present? false
Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.