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() methodimportjava.util.*; publicclassLinked_Hash_Map_Demo {    publicstaticvoidmain(String[] args)    {         // Creating an empty LinkedHashMap        LinkedHashMap<Integer, String> li_hash_map =         newLinkedHashMap<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));    }} | 
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() methodimportjava.util.*; publicclassHash_Map_Demo {    publicstaticvoidmain(String[] args)    {         // Creating an empty LinkedHashMap        LinkedHashMap<String, Integer> li_hash_map =         newLinkedHashMap<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"));    }} | 
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.
 


 
                                    







