IdentityHashMap containsKey() Method in Java

Last Updated : 23 Jul, 2018

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() method 
import 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)); 
    } 
} 
 
  

Output:

  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() method 
import 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")); 
    } 
} 
 
  

Output:

  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.

IdentityHashMap containsValue() Method in Java

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