This print for content only-size & color not accurate 7" X 9-1/4" / casebound / malloy

// This time, throw an exception if the user speeds up beyond MaxSpeed.

public void Accelerate(int delta)

{

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8849CH07.qxd  10/1/07  10:38 AM  Page 224

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if (carIsDead)

Console.WriteLine("{0} is out of order...", petName);

else

{

currSpeed += delta;

if (currSpeed >= MaxSpeed)

{

carIsDead = true;

currSpeed = 0;

// Use the "throw" keyword to raise an exception.

throw new Exception(string.Format("{0} has overheated!", petName));

}

else

Console.WriteLine("=> CurrSpeed = {0}", currSpeed);

}

}

Before examining how a caller would catch this exception, a few points of interest. First of all,

when you are throwing an exception, it is always up to you to decide exactly what constitutes the

error in question, and when it should be thrown. Here, you are making the assumption that if the

program attempts to increase the speed of a car that has expired, a System.Exception type should

be thrown to indicate the Accelerate() method cannot continue (which may or may not be a valid

assumption).

Alternatively, you could implement Accelerate() to recover automatically without needing to

throw an exception in the first place. By and large, exceptions should be thrown only when a more

terminal condition has been met (for example, not finding a necessary file, failing to connect to a

database, and whatnot). Deciding exactly what constitutes throwing an exception is a design issue

you must always contend with. For our current purposes, assume that asking a doomed automobile

to increase its speed justifies a cause to throw an exception.