Implementing a phonebook using HashMap in Java

23 Oct 2023

HashMap

In this blog post, we will explore how to implement a phonebook using the HashMap data structure in Java. A phonebook is a collection that allows us to store and retrieve phone numbers based on the associated names. The HashMap provides an efficient way to perform these operations with constant time complexity (O(1)).

Let’s get started!

Creating a Phonebook
Adding Contacts
Searching for Contacts
Updating Contacts
Removing Contacts
Conclusion

Creating a Phonebook

First, we need to create a new HashMap instance to serve as our phonebook. We will use the person’s name as the key and their corresponding phone number as the value.

import java.util.HashMap;

public class Phonebook {

    private HashMap<String, String> contacts;

    public Phonebook() {
        contacts = new HashMap<>();
    }

    // Other methods can be implemented here
}

In the above code, we have defined a Phonebook class with a HashMap instance named contacts.

Adding Contacts

To add a contact to the phonebook, we simply need to put the name and phone number into the contacts map using the put() method.

public void addContact(String name, String phoneNumber) {
    contacts.put(name, phoneNumber);
}

Searching for Contacts

To search for a contact in the phonebook, we can use the get() method of HashMap by providing the name of the contact as the key.

public String searchContact(String name) {
    return contacts.get(name);
}

The above method returns the phone number associated with the given name, or null if the contact does not exist in the phonebook.

Updating Contacts

To update a contact’s phone number in the phonebook, we can simply reassign the value associated with the given name.

public void updateContact(String name, String newPhoneNumber) {
    contacts.put(name, newPhoneNumber);
}

Removing Contacts

To remove a contact from the phonebook, we can use the remove() method of HashMap by providing the name of the contact as the key.

public void removeContact(String name) {
    contacts.remove(name);
}

Conclusion

In this blog post, we have learned how to implement a phonebook using the HashMap data structure in Java. We explored adding, searching, updating, and removing contacts from the phonebook. Using HashMap provides an efficient way to manage a phonebook with constant time complexity for most operations.

Make sure to check out the official Java HashMap documentation for more information and advanced usage.

Happy coding! #Java #HashMap

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