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The withdrawMoney method has a assert statement that checks whether the balance is grater than or equal to amount to be withdrawn.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

licensed cleaning services Park Ridge ..

In The News:

Chrome extension spyware disguised as a free VPN service highlights security risks after it captured private browsing data from trusted sites.

New research shows how fatty acids in cooking oil can safely dissolve and recover silver from circuit boards without harmful chemicals or environmental damage.

The Fox News AI newsletter gives you information on the latest AI technology advancements, and about the challenges and opportunities AI presents now and for the future.

Anthropic investigates alarming AI abuse case where hacker automated entire cybercrime campaign using Claude, stealing sensitive data from defense and healthcare firms.

TikTok, Meta and YouTube restrict Charlie Kirk shooting videos with age gates and warnings while X faces criticism for allowing continued circulation.

Cybercriminals use fake troubleshooting websites to trick Mac users into running terminal commands that install Shamos malware through ClickFix tactics.

San Francisco startup Fable launches Showrunner, an AI platform dubbed the 'Netflix of AI' that generates animated episodes from text descriptions with Amazon support.

Apple raised iPhone prices for some models despite receiving tariff relief from President Donald Trump, with the new lineup starting at $799 for the base model.

A two-story 3D concrete printed home in Western Australia demonstrates faster construction methods that could reshape American housing amid rising costs.

Credit scores remain important during retirement for insurance rates and housing applications, while seniors become prime targets for identity theft and financial scams.

Scammers now send unexpected packages with QR codes that redirect victims to fraudulent websites or download malicious software to steal sensitive information.

Meeting AI tools record private conversations alongside work discussions, creating privacy risks that can be managed with proper settings and awareness.

Hotel privacy concerns are valid but rare, with methods to detect hidden tech using smartphone flashlights, mirror tests and scanning apps.

Improve your Wi-Fi speed and reliability with 10 simple router optimization tips that don't require special apps or expensive subscriptions.

A Columbia University breach exposed names, Social Security numbers and academic records of nearly 869,000 people, with notifications beginning in August.

Rental car drivers use AI-powered apps like Proofr to protect themselves from unfair damage fees as major companies deploy automated inspection tools.

Fox News' AI newsletter brings you the latest on technology advancements around artificial intelligence.

OnTrac data breach between April 13-15, 2025, exposed personal information of over 40,000 people including Social Security numbers and medical records.

A woman named Wika announces her engagement to an AI chatbot sparking worldwide debate about virtual relationships and technology.

The notorious people search site National Public Data relaunches despite a previous breach affecting 3 billion individuals, raising fresh privacy concerns.

Revolutionary TRAUMAGEL gel controls life-threatening bleeding from gunshot wounds and traumatic injuries, helping first responders prevent prehospital deaths.

Protect your home network by enabling proper encryption, creating strong passwords, checking connected devices and using VPN and antivirus software.

The Navy's solar-powered Skydweller drone flew nonstop for 73 hours in Mississippi, proving renewable energy can power long-endurance military missions.

Moving and downsizing expose seniors to identity theft and scams as data brokers collect real estate records and personal information to sell to criminals.

ShengShu's Vidar technology revolutionizes humanoid robot training by using AI-generated synthetic video, reducing required training data from hours to just 20 minutes.

Assertion in Java

Software