10.2 Performance Impact of Exception Handling
In general, wrapping
your Java code with try/catch blocks doesn't have a
significant performance impact on your applications. Only when
exceptions actually occur is there a negative performance impact,
which is due to the lookup the JVM must perform to locate the proper
handler for the exception. If the catch block for the exception is
located in the same method, the impact is not so bad. However, the
further down the call stack the JVM has to go to find the exception
handler, the greater the impact becomes.This is why you should use a try/catch block only for error
conditions. You should never use exceptions for things such as
controlling program flow. The following use of a try/catch block is
probably fine, but it's getting very close to
improper use of exception handling:Double basePrice = null;
String basePriceStr = request.getParameter( "BASE_PRICE_AMOUNT" );
// Use a try/catch to make sure the value is a number
try{
basePrice = Double.valueOf( basePriceStr );
}catch( NumberFormatException ex ){
// The value could not be converted to a valid Double; set the default
basePrice = ApplicationDefaults.DEFAULT_BASE_PRICE;
} The previous code fragment shows a try/catch block determining an
error condition and taking corrective action. The error condition is
an invalid price value, and the corrective action is to assign a
default value. There are other ways to determine whether a string is
a valid Double value, but using this approach is
fairly popular. Fortunately, the exception handler is located in the
same method, and the JVM doesn't incur a large
penalty for this occurrence.Of course, rules are always somewhat subjective, and what is a valid
reason to one developer may not be to another. You should be aware of
the drawbacks and avoid using try/catch blocks other than for actual
error conditions. |
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