Swing uses quite a bit of memory, which is true, but I would not qualify it as a "burst of memory."
As one answer says, in Swing, each component is written on its own (without using the original OS widgets), this is what makes Swing portable via platforn.
The Look'n'Feel concept, from my point of view, is very good, but it has, of course, some drawbacks (memory consumption). But I believe that this drawback is largely balanced by the ability to instantly change the appearance of the application with only one line of code. There is clarity of third-party look'n'feels (some commercial, some open source) that can give your application a “friendly” look.
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