The AbstractMap.containsKey() method is used to check whether a particular key is being mapped into the AbstractMap or not. It takes the key element as a parameter and returns True if that element is mapped in the map.
Syntax:
AbstractMap.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 AbstractMap.containsKey() Method:
Program 1: Mapping String Values to Integer Keys.
// Java code to illustrate the containsKey() method import java.util.*;
public class Abstract_Map_Demo {
public static void main(String[] args)
{
// Creating an empty AbstractMap
AbstractMap<Integer, String>
abs_map = new HashMap<Integer, String>();
// Mapping string values to int keys
abs_map.put( 10 , "Geeks" );
abs_map.put( 15 , "4" );
abs_map.put( 20 , "Geeks" );
abs_map.put( 25 , "Welcomes" );
abs_map.put( 30 , "You" );
// Displaying the AbstractMap
System.out.println( "Initial Mappings are: "
+ abs_map);
// Checking for the key_element '20'
System.out.println( "Is the key '20' present? "
+ abs_map.containsKey( 20 ));
// Checking for the key_element '5'
System.out.println( "Is the key '5' present? "
+ abs_map.containsKey( 5 ));
}
} |
Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 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 Abstract_Map_Demo {
public static void main(String[] args)
{
// Creating an empty AbstractMap
AbstractMap<String, Integer>
abs_map = new HashMap<String, Integer>();
// Mapping int values to string keys
abs_map.put( "Geeks" , 10 );
abs_map.put( "4" , 15 );
abs_map.put( "Geeks" , 20 );
abs_map.put( "Welcomes" , 25 );
abs_map.put( "You" , 30 );
// Displaying the AbstractMap
System.out.println( "Initial Mappings are: "
+ abs_map);
// Checking for the key_element 'Welcomes'
System.out.println( "Is the key"
+ " 'Welcomes' present? "
+ abs_map.containsKey( "Welcomes" ));
// Checking for the key_element 'World'
System.out.println( "Is the key"
+ " 'World' present? "
+ abs_map.containsKey( "World" ));
}
} |
Initial Mappings are: {4=15, Geeks=20, You=30, Welcomes=25} 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.