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