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What is the Hashtable.values() method in Java?

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Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

A hash table is a collection of key-value pairs. The object to be used as a key should implement the hashCode and equals methods, and the key and the value should not be null.

You can read the difference between HashTable and HashMap here.

What is the values() method in HashTable?

The values() method of the HashTable class returns the Collection view of the values present in a HashTable object.

Syntax

public Collection<V> values()

This method doesn’t take an argument.

Code

The following code demonstrates how to use the values() method.

import java.util.Hashtable;
import java.util.Collection;
class ValuesExample {
public static void main(String[] args) {
// create a Hashtable
Hashtable<Integer, String> numbers = new Hashtable<>();
numbers.put(1, "One");
numbers.put(2, "Two");
System.out.println("The Hashtable is - " + numbers);
Collection<String> values = numbers.values();
System.out.println("The values in Hashtable is - " + values);
numbers.put(3, "Three");
System.out.println("The values in Hashtable is - " + values);
}
}

Explanation

In the code above:

  • In line 1, we imported the Hashtable class.

  • In line 7, we created a HashTable object with the name numbers.

  • In lines 9 and 10, we used the put() method to add two mappings ({1=one, 2=two}) to the HashTable object.

  • In line 13, we used the values() method of HashTable to get the values present in numbers.

  • In line 16, we added a new entry (3, "Three") to the HashTable object.

  • In line 17, we printed the values variable. The newly added entry Three will be automatically available in the values variable without the need to call the values() method because the previous call to the values() method returned the Collection view.

RELATED TAGS

hashtable
values
java
communitycreator

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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