Hashtable containsValue(Object) in Java

containsValue(Object): This method is available in java.util.Hashtable class of Java.

Syntax:

boolean java.util.Hashtable.containsValue(Object value)

This method takes one argument. This method returns true if this hashtable maps one or more keys to this value.

Parameters: One parameter is required for this method.

value: value whose presence in this hashtable is to be tested.

Returns: true if this map maps one or more keys to the specified value.

Throws:

NullPointerException - if the value is null.

Approach 1: When no exception

Java

import java.util.Hashtable;

public class HashtablecontainsValue {
    public static void main(String[] args) {
        Hashtable<String, Integer> hashtable =
                    new Hashtable<String, Integer>();

        hashtable.put("Hello", 1);
        hashtable.put("World", 2);

        Integer value = 1;

        System.out.println(hashtable.containsValue(value));

    }
}

Output:

true

Approach 2: NullPointerException

Java

import java.util.Hashtable;

public class HashtablecontainsValue {
    public static void main(String[] args) {
        Hashtable<String, Integer> hashtable = 
                       new Hashtable<String, Integer>();

        hashtable.put("Hello", 1);
        hashtable.put("World", 2);

        Integer value = null;

        System.out.println(hashtable.containsValue(value));

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException
	at java.base/java.util.Hashtable.contains(Hashtable.java:311)
	at java.base/java.util.Hashtable.containsValue(Hashtable.java:338)