LinkedHashMap containsKey() Method in Java with Examples

Last Updated : 18 Nov, 2021

The java.util.LinkedHashMap.containsKey() method is used to check whether a particular key is being mapped into the LinkedHashMap or not. It takes the key element as a parameter and returns True if that element is mapped in the map.
Syntax:

Linked_Hash_Map.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 Type: The method returns boolean true if the presence of the key is detected else false.

Example 1: Mapping String Values to Integer Keys.

Java

// Java code to illustrate the containsKey() method
import java.util.*;

public class Linked_Hash_Map_Demo {
    public static void main(String[] args)
    {

        // Creating an empty LinkedHashMap
        LinkedHashMap<Integer, String> li_hash_map = 
        new LinkedHashMap<Integer, String>();

        // Mapping string values to int keys
        li_hash_map.put(10, "Geeks");
        li_hash_map.put(15, "4");
        li_hash_map.put(20, "Geeks");
        li_hash_map.put(25, "Welcomes");
        li_hash_map.put(30, "You");

        // Displaying the LinkedHashMap
        System.out.println("Initial Mappings are: " + li_hash_map);

        // Checking for the key_element '20'
        System.out.println("Is the key '20' present? " + 
        li_hash_map.containsKey(20));

        // Checking for the key_element '5'
        System.out.println("Is the key '5' present? " + 
        li_hash_map.containsKey(5));
    }
}

Output:

Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
Is the key '20' present? true
Is the key '5' present? false

Example 2: Mapping Integer Values to String Keys.

Java

// Java code to illustrate the containsKey() method
import java.util.*;

public class Hash_Map_Demo {
    public static void main(String[] args)
    {

        // Creating an empty LinkedHashMap
        LinkedHashMap<String, Integer> li_hash_map = 
        new LinkedHashMap<String, Integer>();

        // Mapping int values to string keys
        li_hash_map.put("Geeks", 10);
        li_hash_map.put("4", 15);
        li_hash_map.put("Geeks", 20);
        li_hash_map.put("Welcomes", 25);
        li_hash_map.put("You", 30);

        // Displaying the LinkedHashMapHashMap
        System.out.println("Initial Mappings are: " + li_hash_map);

        // Checking for the key_element 'Welcomes'
        System.out.println("Is the key 'Welcomes' present? " + 
        li_hash_map.containsKey("Welcomes"));

        // Checking for the key_element 'World'
        System.out.println("Is the key 'World' present? " + 
        li_hash_map.containsKey("World"));
    }
}

Output:

Initial Mappings are: {Geeks=20, 4=15, Welcomes=25, You=30}
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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