[was : Re: Cross platform: How they do it?] Java memory management

[James McDonald]

I'm always afraid when people mention memory management in Java. Because

>>poorly coded applications in Java are worse than equivalent packages in
>>Visual Basic.
>>
>>Theoretically, you can let Java's Virtual Machine take care of the
>>memory. Just create any number of objects you want and eventually, the
>>garbage collector will kick in and clear all the unused or expired
>>objects away. There are problems with this approach.
>>
>>A useful analogy that comes to mind is the way my wife and I handle
>>housework. Because we have no kids and no maid, housework will have to
>>be done by one of us. My wife takes out a clean cup everytime she needs
>>a drink, which adds up to quite a number of dirty cups by the end of the
>>day. Theoretically, I should clean the cups at the end of every day
>>before all the clean cups get used (because I'm not working), and
>>therefore ensure that there are plenty of clean cups the next day. Well,
>>when 6 pm comes around, and I'm working on a problem (or playing
>>Warcraft), guess what ? I have to drop everything and do the cups.
>>
>>The Java garbage collector, especially in Sun's Java VM, does the same
>>thing. If you leave memory management to the Java VM, eventually, when
>>it does kick in, because memory is low, you will find that your
>>application "hangs up" -- literally stops responding, until the garbage
>>collector finishes its task of re-claiming unused memory. This time can
>>be quite significant (up to minute, once when I was doing a presentation
>>to venture capitalists !) if you have a lot of memory that needs to be
>>cleaned up.
>>
>>There is no explicit concept of pointers in Java, such as you find in C.
>>But there are ways that you can make sure that objects you create are
>>disposed of, by setting them to null, or using the close() method if it
>>is available. This affects the programmer in a couple of ways: for
>>novice programmers working on small projects for a small audience
>>(example: a school lab project), this means that they can concentrate on
>>the logic, and understand the language, without worrying about memory.
>>This means higher productivity and a less steep learning curve. For
>>larger projects, however, you'll quickly find that the garbage collector
>>is no substitute for some defensive programing techniques.
>>    
>>
Well this explains why  some java apps at work are dogs.