Last updated
December 6, 2023

Java Phone Number Validation Guide

Samuel Rays

Table of Contents:

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Phone number validation is a crucial aspect of programming, especially when dealing with user input or communication-related functionalities in applications. Ensuring that phone numbers adhere to certain standards helps maintain data integrity, enhances user experience, and facilitates seamless communication. It’s common for some users to unintentionally type in invalid phone numbers. In this article, I’d be taking you through the art of phone number validation in Java, and you'll be well on your way to getting all your validation issues resolved whether you're developing a sleek online form, a mobile app, or any other code-driven creation that is for phone digits.

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Understanding Java Regex for Validation:

If you are in the Java’s beginners category you may, and may not have heard of Regex before, so let me give you a short tutorial about regular expressions. These are expressions that allow you to characterize a group of strings according to the traits that all of the strings in the group have in common. To build regular expressions, you need to master a specific syntax that goes beyond the Java programming language's standard grammar. The intricacy of regular expressions varies, but you can decode (or write) any regular expression if you grasp the fundamentals of its construction. There are numerous varieties of regular expressions available, including grep, Perl, Tcl, Python, PHP, and awk. The java.util.regex API's regular expression syntax is most comparable to that of Perl.

Regex is a widely used tool in Java for phone number validation. A character sequence that defines a search pattern is called a regex pattern. Regex patterns allow us to specify the format and hierarchy that a legitimate phone number must adhere to.

Understanding the general patterns and phone number formats used in various locations is necessary to identify valid phone numbers in Java using Regex.

How the Java.Util.Regex API works

Three classes make up the majority of the java.util.regex package: Pattern, Matcher, and PatternSyntaxException.

A regular expression's compiled representation is called a Pattern object. There are no public constructors offered by the Pattern class. One of its public static compile methods must be called to construct a pattern; this method will produce a Pattern object.

The engine that deciphers the pattern and applies match operations to an input string is called a Matcher object. The Matcher class does not define any public constructors, similar to the Pattern class. By calling the p.matcher method on a Pattern object, you can get a Matcher object.

An unchecked exception that indicates a syntax issue in a regular expression pattern is called a PatternSyntaxException object.

Now let's look at how to verify phone numbers, specifically those from India and the US, which are frequently used.

Validating Indian Phone Numbers in Java

Indian phone number formats have specific patterns that need to be considered during the validation process. In this section, I will focus on how core Java can be used to validate Indian phone numbers. I will provide code examples and explain the regex pattern for Indian mobile numbers, taking into account variations in formats and regional codes. The standard format for Indian phone numbers is a 10-digit numeric sequence. However because different locations and mobile service providers have distinct formats, there are differences in them. Typical patterns include the following:

  • 10-digit mobile numbers starting with prefixes such as 9, 8, 7, or 6.
  • Landline numbers with area codes and 8-digit subscriber numbers.

Variations such as the addition of the "0" prefix before the mobile number or the country code "+91" are supported by this regex pattern. It also takes into consideration other separators, such as spaces and hyphens.

Validating USA Phone Numbers in Java

The format for USA phone numbers is well-defined and includes subscriber numbers and area codes; it is usually a seven-digit subscriber number followed by a three-digit area code. We'll look at using Java regex to validate USA phone numbers in this part. In addition to explaining the regex pattern and giving code examples, I'll go over alternatives including parentheses and hyphens for USA numbers. You can incorporate precise phone number validation for USA numbers into your Java apps by adhering to the instructions and examples given. To validate USA phone numbers, you can try utilizing the following pattern with Java regex:

Using parentheses around the area code and hyphens or dots to separate distinct portions of the given phone number are among the forms that may be achieved with this regex pattern.

Using AbstractAPI's Phone Number Validation API

An easy-to-use and dependable API for phone number validation is provided by AbstractAPI. We'll walk you through using Java to leverage AbstractAPI's Phone Number Validation API in this part. Getting an API key, setting up the client, submitting queries to the API, and deciphering the validation response are all steps that we will walk you through. You may streamline the phone number validation procedure in your Java apps by utilizing AbstractAPI's API.

Step 1: Visit the AbstractAPI website to register and get an API key.

Step 2: Include the Java client library for AbstractAPI as a dependency in your project to install it.

Step 3: Begin the initialization process of the AbstractAPI client with your API key.

Step 4: Send a request to the Phone Number Validation API via the client, including the phone number you wish to validate.

Step 5: Verify the validity of the phone number by looking at the API's response.

Using Google's libphonenumber Library

One library you may grab from Github to incorporate in the code of your application or website is Google's libphonenumber. The package includes methods and functions that assist you in identifying valid phone number, be they domestic or international phone numbers. You can check out our “How Does Google Phone Number Validator Work?” article to get the step-by-step guide.

Here’s a snippet to activate Google's libphonenumber Library

Common Validation Scenarios

There are a few typical scenarios and things to bear in mind while validating phone numbers in Java:

  1. Managing international phone numbers: You might need to take into account various country codes and formats to verify international phone numbers. International phone numbers can be accommodated by modifying regex patterns, or they can be handled automatically by libraries such as libphonenumber.
  2. Eliminating formatting characters: Characters such as hyphens, parentheses, or spaces can be used when entering phone numbers. To guarantee correct results, these characters must be eliminated before validation.
  3. Managing extensions: Phone numbers that have extensions, usually denoted by "x" or "ext," need to be verified further. Your validation logic can be changed to handle extensions differently.
  4. Verifying landline numbers: You might also need to confirm landline numbers in addition to mobile ones. Take into account the unique patterns and forms associated with landline numbers in your intended area.


This article has covered the idea of Java phone number validation regardless if you are using the Java 8 or Java 21 version, how to use regex patterns to validate  USA and Indian phone numbers, and step-by-step instructions for utilizing AbstractAPI's Phone Number Validation API. Additionally, I've outlined typical validation scenarios and things to think about when putting phone number validation into practice in Java.

By adopting these techniques and tools into your Java projects, you will improve the overall user experience and data quality of your applications by ensuring the accuracy and dependability of phone number data.


What is the purpose of using Abstract's Phone Number Validation API in Java?

Abstract's Phone Number Validation API is designed to ensure the accuracy and format compliance of phone numbers in Java applications. It streamlines the validation process, reduces errors in user input, and enhances overall data integrity, making it invaluable for applications requiring reliable communication.

Can Abstract's API validate international phone numbers, including those from the USA and India?

Yes, Abstract's Phone Number Validation API is equipped to handle and validate international phone numbers, including various formats from the USA, India, and other countries. It can accurately distinguish between different country codes and formats, ensuring comprehensive validation.

Is it difficult to integrate Abstract's Phone Number Validation API into existing Java applications?

Integration of Abstract's API into Java applications is straightforward. It requires registering for an API key, including the Java client library in your project, initializing the client with your API key, and sending validation requests. The process is well-documented and designed for ease of use.

Samuel Rays
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