Home
>
Software
>
Assertion in Java

Assertion in Java

Assertion facility is added in J2SE 1.4. In order to support this facility J2SE 1.4 added the keyword assert to the language, and AssertionError class. An assertion checks a boolean-typed expression that must be true during program runtime execution. The assertion facility can be enabled or disable at runtime.

Declaring Assertion

Assertion statements have two forms as given below

assert expression;

assert expression1 : expression2;

The first form is simple form of assertion, while second form takes another expression. In both of the form boolean expression represents condition that must be evaluate to true runtime.

If the condition evaluates to false and assertions are enabled, AssertionError will be thrown at runtime.

Some examples that use simple assertion form are as follows.

assert value > 5 ;

assert accontBalance > 0;

assert isStatusEnabled();

The expression that has to be asserted runtime must be boolean value. In third example isStatusEnabled() must return boolean value. If condition evaluates to true, execution continues normally, otherwise the AssertionError is thrown.

Following program uses simple form of assertion

//AssertionDemo.java

Class AssertionDemo{

Public static void main(String args[]){

System.out.println( withdrawMoney(1000,500) );

System.out.println( withdrawMoney(1000,2000) );

}

public double withdrawMoney(double balance , double amount){

assert balance >= amount;

return balance ? amount;

}

In above given example, main method calls withdrawMoney method with balance and amount as arguments. The withdrawMoney method has a assert statement that checks whether the balance is grater than or equal to amount to be withdrawn. In first call the method will execute without any exception, but in second call it AssertionError is thrown if the assertion is enabled at runtime.

Enable/Disable Assertions

By default assertion are not enabled, but compiler complains if assert is used as an identifier or label. The following command will compile AssertionDemo with assertion enabled.

javac ?source 1.4 AssertionDemo.java

The resulting AssertionDemo class file will contain assertion code.

By default assertion are disabled in Java runtime environment. The argument ?eanbleassertion or ?ea will enables assertion, while ?disableassertion or ?da will disable assertions at runtime.

The following command will run AssertionDemo with assertion enabled.

Java ?ea AssertionDemo

Java ?enableassertion AssertionDemo

Second form of Assertion

The second form of assertion takes another expression as an argument.

The syntax is,

assert expression1 : expression2;

where expression1 is the condition and must evaluate to true at runtime.

This statement is equivalent to

assert expression1 : throw new AssertionError(expression2);

Note: AssertionError is unchecked exception, because it is inherited from Error class.

Here, expression2 must evaluate to some value.

By default AssertionError doesn't provide useful message so this form can be helpful to display some informative message to the user.

Rahim Vindhani
Application Develper [Application Development & Webservices]
IBM Global Services, pune, India
email: rahim.vindhani@gmail.com
web: http://www.rahim.co.nr

bathroom cleaning service Northbrook ..

In The News:

ETA sharing on Apple Maps and Google Maps keeps contacts updated automatically while you drive safely. Learn step-by-step instructions for iPhone and Android.

Data removal from brokers protects against AI-powered scams and deepfake threats in 2026. Learn how data brokers sell your personal information to scammers.

Learn how to act against cybercriminals in 2026 with essential security steps like two-factor authentication, software updates and credit freezing.

Choose between OpenAI releasing Sora text-to-video model, the AI race heating up, or Waymo driverless cars launching in cities across the country

Learn how to set up Google Maps and Apple Maps on your phone to automatically remember where you parked. Step-by-step instructions for enabling location services and parking detection.

Phishing scammers use rnicrosoft.com domain to impersonate Microsoft by replacing "m" with "rn" in typosquatting attacks that steal login credentials.

OpenAI announces new teen safety rules for ChatGPT users under 18, blocking romantic roleplay and requiring extra caution on body image topics.

A 2025 data breach at fintech company 700Credit exposes personal information of more than 5.8 million people through compromised third-party integration partner.

Retailers lose $76.5 billion annually to return fraud as nearly 10% of U.S. retail returns involve fraudulent activity, with $850 billion in returns expected in 2025.

ShinyHunters claims responsibility for stealing 94GB of Pornhub user data affecting over 200 million records and demands Bitcoin ransom.

ChatGPT 2025 now connects to Apple Music, Canva, Expedia, TripAdvisor and OpenTable through built-in apps that help users create playlists, design graphics and more.

Apple releases emergency patches for two zero-day vulnerabilities actively exploited in attacks. iPhone and iPad users urged to update immediately.

DoorDash launches Zesty, an AI-powered social app that recommends restaurants through conversational search, now testing in San Francisco and New York.

Cybersecurity firm Infoblox reveals that over 90 percent of parked domains now redirect visitors to scams and malware, making simple typos extremely dangerous.

The Fox News AI Newsletter covers the latest artificial intelligence technology advancements, including the challenges and opportunities AI presents now and for the future.

GPT-5.2 is now live for all ChatGPT users with improved coding, writing and image interpretation, with Kurt Knutsson offering his review.

New iPhone replacement scam uses pressure tactics and fake carrier calls to steal devices from buyers. Criminals claim shipping errors and demand urgent returns.

Amazon Ring's new facial recognition feature sparks privacy controversy as Electronic Frontier Foundation critics argue the AI upgrade expands surveillance risks.

New Android banking trojan Sturnus steals credentials, reads encrypted messages and controls devices.

Denmark's 3D-printed student village proves automation builds 36 apartments faster than traditional methods. Skovsporet project shows housing future.

Discover Android's new Sound Notifications feature that alerts you to smoke alarms, doorbells, and baby cries even when wearing headphones.

New SantaStealer malware reportedly threatens holiday shoppers with password theft. This Christmas-themed info-stealer targets browsers and crypto wallets.

The Christmas season brings a surge in Netflix phishing scams targeting shoppers with fake emails. Stacey P received convincing scam but verified account first.

San Francisco Giants invite Jamie Grohsong to throw ceremonial first pitch at Oracle Park after he learned to play baseball with a bionic hand following an injury.

FBI warns cybercriminals are stealing family photos from social media to create fake proof of life images in virtual kidnapping scams targeting victims.

Assertion in Java

Software