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() methodimport 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() methodimport 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
