Hashtable contains() Method in Java (original) (raw)

Last Updated : 2 Jun, 2023

The java.util.Hashtable.contains(Object value) method in Java is used to check whether a particular value is being mapped by any keys present in the Hashtable.

Syntax:

Hash_table.contains(Object value)

Parameters: The method accepts one parameter value of object type and refers to the value of the hashtable whose mapping is to be verified.

Return Value: The method returns a boolean true value if the passed value is mapped by any of the keys in the Hashtable. Exceptions: The method throws NullPointerException if the passed value is Null.

Below programs illustrate the working of the above-mentioned method:

Program 1:

Java `

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

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

    // Creating an empty Hashtable
    Hashtable<Integer, String> hash_table = 
    new Hashtable<Integer, String>();

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

    // Displaying the HashMap
    System.out.println("Initial Table is: " + hash_table);

    // Checking for the Value 'Geeks'
    System.out.println("Is the value 'Geeks' present? " + 
    hash_table.contains("Geeks"));

    // Checking for the Value 'World'
    System.out.println("Is the value 'World' present? " + 
    hash_table.contains("World"));
}

}

`

Output:

Initial Table is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes} Is the value 'Geeks' present? true Is the value 'World' present? false

Program 2:

Java `

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

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

    // Creating an empty Hashtable
    Hashtable<String, Integer> hash_table = 
    new Hashtable<String, Integer>();

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

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

    // Checking for the Value '10'
    System.out.println("Is the value '10' present? " + 
    hash_table.containsValue(10));

    // Checking for the Value '30'
    System.out.println("Is the value '30' present? " + 
    hash_table.containsValue(30));

    // Checking for the Value '40'
    System.out.println("Is the value '40' present? " + 
    hash_table.containsValue(40));
}

}

`

Output:

Initial Mappings are: {You=30, Welcomes=25, 4=15, Geeks=20} Is the value '10' present? false Is the value '30' present? true Is the value '40' present? false