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Java Performance Urban Legends
An anonymous reader writes "Urban legends are kind of like mind viruses; even though we know they are probably not true, we often can't resist the urge to retell them (and thus infect other gullible "hosts") because they make for such good storytelling. Most urban legends have some basis in fact, which only makes them harder to stamp out. Unfortunately, many pointers and tips about Java performance tuning are a lot like urban legends -- someone, somewhere, passes on a "tip" that has (or had) some basis in fact, but through its continued retelling, has lost what truth it once contained. This article examines some of these urban performance legends and sets the record straight."
I wonder to what extent this exists in other languages? For example, there is an oft-cited tip that says using persistent database applications with LAMP applications increases performance. I've found in actual practice that this depends on a lot of factors such as server load, amount of available memory, etc.
I remember in my Turbo Pascal programming days (heh) that a lot of people said that using Units would degrade performance. So I tried it both ways and it never really made a difference, for my applications anyways.
I'd say before taking someone's word for it on a performance enhancing technique, test it out. Because not everything you read is true, and not everything you read will apply to every environment or every application.
My journal has hot
Exactly how does "string require careful attention"? I've seen this statement a couple of times, but only to suspect that many people don't really understand what Java Strings are.
The first mistake, of course, is that people think that (a == b) == a.equals(b) which is, of course, only true if a and b are constant strings or one have invoked intern() on them.
The second is to not realize that string concatenation with the "+" operator is a special case and only syntactic sugar for StringBuffer operations. Thus, someone not familiar with Java may accidentally generate huge amount of StringBuffer objects in loops.
However, both these things are very fundamental Java knowledge and among the first thing you learn when studying Java. It's obvious that you don't start coding serious Java without knowing how try..catch..finally works, and equally obvious that you should the know about the deals with the String class.
I wonder to what extent this exists in other languages?
Probably lots. Everywhere.
As a crude approximation, 90% of the time is due to 10% of the code. Improving the "efficiency" of the 90% of the code that is responsible for only 10% of the time tends to be counter-productive. Of course there are no easy magic rules for how to improve the 10% of the code that is responsible for 90% of the time, or even identify exactly what that 10% really is.
What does work is to have a sense of how long things should take and find and cure whatever is taking much longer than it should.