A HashTable is a collection of key-value pairs. The object to be used as a key should implement the hashCode
and equals
method, and the key and the value should not be null
.
You can read more about the difference between
HashTable
andHashMap
here.
The contains
method of Hashtable
is used to check if a specified value is present in the Hashtable
object.
public boolean contains(Object value)
The value to be checked for presence is passed as an argument.
This method throws NullPointerException
if the argument is null
.
This method returns true
if the value has one or more keys mapping. Otherwise, false
is returned.
The below example shows how to use the contains
method.
import java.util.Hashtable;class HashtableContainsExample {public static void main( String args[] ) {Hashtable<Integer, String> map = new Hashtable<>();map.put(1, "one");map.put(2, "two");System.out.println("\nChecking if the value 'one' is present : "+ map.contains("one"));System.out.println("\nChecking if the value 'three' is present : "+ map.contains("three"));}}
In the code above:
In line 1, we import the Hashtable
class.
In line 4, we create a Hashtable
object with the name map
.
In lines 5 and 6, we use the put
method to add two mappings ({1=one, 2=two}
) to the map
object.
In line 7, we use the contains
method to check if the map
has a key mapping for the value "one"
. true
is returned as a result because the key 1
is mapped to the value "one"
.
In line 8, we use the contains
method to check if the map
has a key mapping for the value "three"
. false
is returned as a result because no key is mapped for the value "three"
.