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_elementthat 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
// 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
// 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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