AbstractMap containsKey() Method in Java with Examples
Last Updated :
24 Oct, 2018
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
// 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));
}
}
Output:
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
// 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"));
}
}
Output:
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.