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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:

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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.




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