The java.util.IdentityHashMap.containsKey() method is used to check whether a particular key is being mapped into the IdentityHashMap or not. It takes the key element as a parameter and returns True if that element is mapped in the map.
Syntax:
Identity_HashMap.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 Value: The method returns boolean true if the presence of the key is detected else false .
Below programs are used to illustrate the working of java.util.IdentityHashMap.containsKey() Method:
Program 1: Mapping String Values to Integer Keys.
// Java code to illustrate the containsKey() methodimport java.util.*;  public class Identity_Hash_Map_Demo {    public static void main(String[] args)    {          // Creating an empty IdentityHashMap        IdentityHashMap<Integer, String> identity_hash =                    new IdentityHashMap<Integer, String>();          // Mapping string values to int keys        identity_hash.put(10, "Geeks");        identity_hash.put(15, "4");        identity_hash.put(20, "Geeks");        identity_hash.put(25, "Welcomes");        identity_hash.put(30, "You");          // Displaying the IdentityHashMap        System.out.println("Initial Mappings are: " +                                           identity_hash);          // Checking for the key_element '20'        System.out.println("Is the key '20' present? " +                            identity_hash.containsKey(20));          // Checking for the key_element '5'        System.out.println("Is the key '5' present? " +                             identity_hash.containsKey(5));    }} |
Initial Mappings are: {10=Geeks, 30=You, 20=Geeks, 25=Welcomes, 15=4}
Is the key '20' present? true
Is the key '5' present? false
Program 2: Mapping Integer Values to String Keys.
// Java code to illustrate the containsKey() methodimport java.util.*;  public class Identity_Hash_Map_Demo {    public static void main(String[] args)    {          // Creating an empty IdentityHashMap        IdentityHashMap<String, Integer> identity_hash =                      new IdentityHashMap<String, Integer>();          // Mapping int values to string keys        identity_hash.put("Geeks", 10);        identity_hash.put("4", 15);        identity_hash.put("Geeks", 20);        identity_hash.put("Welcomes", 25);        identity_hash.put("You", 30);          // Displaying the IdentityHashMap        System.out.println("Initial Mappings are: " +                                               identity_hash);          // Checking for the key_element 'Welcomes'        System.out.println("Is the key 'Welcomes' present? " +                         identity_hash.containsKey("Welcomes"));          // Checking for the key_element 'World'        System.out.println("Is the key 'World' present? " +                            identity_hash.containsKey("World"));    }} |
Initial Mappings are: {Geeks=20, Welcomes=25, You=30, 4=15}
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.
