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