Enthuware

3. Should not be used for side effects. For example:    

Code: Select all

public boolean doSomething()    
{     
 ...
}    

public void someMethod()    
{       
   assert doSomething();    
}  

This is not a proper use because here the assertion is used for its side effect of calling of the doSomething() method.

public void openSocket(int port) {     
   Socket s = //valid code to open socket here     
   ...     
   assert s != null; 
}

Assertions should be used for:
...
3. Validating post conditions at the end of any method. This means, after executing the business logic, you can use assertions to ensure that the internal state of your variables or results is consistent with what you expect. For example, a method that opens a socket or a file can use an assertion at the end to ensure that the socket or the file is indeed opened.

But why "at the end"? What's the idea? If code to open socket fails for some reason and variable "s" is null, then I got some exception (checked or unchecked) in business logic and won't reach assertion.

admin wrote:That's the whole point of assertions. They produce outputs that illuminate the parts of code that execute successfully (i.e. without exceptions) yet are producing unexpected results.