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 ));
}
} |
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" ));
}
} |
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.