Dictionary remove(Object) in Java

remove(Object): This method is available in java.util.Dictionary class of Java.

Syntax:

Integer java.util.Dictionary.remove(Object key)

This method takes one argument of type Object as its parameter. This method removes the key (and its corresponding value) from this dictionary.

Note: This method does nothing if the key is not in this dictionary.

Parameters: One parameter is required for this method.

key: the key that needs to be removed.

Returns: the value to which the key had been mapped in this dictionary, or null if the key did not have a mapping.

Throws:

NullPointerException - if key is null.

Approach 1: When no exception

Java

import java.util.Dictionary;
import java.util.Hashtable;

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

        Dictionary<String, Integer> dictionary = 
                         new Hashtable<String, Integer>();

        dictionary.put("Hello", 10);
        dictionary.put("Java", 4);
        dictionary.put("C++", 17);

        dictionary.remove("Hello");

        System.out.println(dictionary);

    }
}

Output:

{Java=4, C++=17}

Approach 2: NullPointerException

Java

import java.util.Dictionary;
import java.util.Hashtable;

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

        Dictionary<String, Integer> dictionary = 
              new Hashtable<String, Integer>();

        dictionary.put("Hello", 10);
        dictionary.put("Java", 4);
        dictionary.put("C++", 17);

        dictionary.remove(null);

        System.out.println(dictionary);

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "Object.hashCode()" because "key" is null
	at java.base/java.util.Hashtable.remove(Hashtable.java:508)