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Java Forum / General / October 2006datastructure performance
Hi there well i need to know something about how java data structures affects performance i need to deal with a huge Vector of element and each element is another big Vector , someone have advised me to use array of vectors instead of what i am doing now which is vector of vectors. ok i understand that using Vector of Vectors will need more memory but will it make the application slower than using Array of Vectors ??!!! ali schreef: > ok i understand that using Vector of Vectors will need more memory but > will it make the application slower than using Array of Vectors ??!!! It will, yes. A Vector essentially wraps around an array, so any operations on a Vector will endure at least one extra (synchronized: cf infra) indirection when compared to an array. Some considerations: - Vector's are only really useful when you do not know in advance the length of your array. If the length is fixed: use an array (certainly when performance is an issue) - If all dimensions are known in advance, why not use an array of arrays? - Only use the Vector class if you need synchronization. If your application is a single-threaded class, you are better of using an ArrayList (even if you need the synchronization overhead, it is probably wiser to use Collections.synchronizedList on an ArrayList) Cheers, Peter > ali schreef: > > ok i understand that using Vector of Vectors will need more memory but [quoted text clipped - 15 lines] > Cheers, > Peter Thanks a lot Peter for your information and advice the reason why i am using Vector is that i dont know the size of array in advance well i know at maximum it could be [256*256] <--- this implies to the outer array and the inner array as well, but i am afraid of holding an array that huge >> ali schreef: >>> ok i understand that using Vector of Vectors will need more memory but [quoted text clipped - 23 lines] > outer array and the inner array as well, but i am afraid of holding an > array that huge Thats tiny. > > the reason why i am using Vector is that i dont know the size of array > > in advance [quoted text clipped - 3 lines] > > > Thats tiny. 64K is indeed a small size for an array -- but not when you have on the order of 64K of them ! To the OP: the structure you use for the outer container won't make very much difference to the speed of your app, and will make no significant difference to the space it takes. However it might be worthwhile considering using raw arrays for the inner lists. Also, if the elements of the inner arrays are numbers -- ints, floats, etc -- which I rather suspect they may be, then you /MUST NOT/ use ArrayLists or Vectors to hold them or your space consumption will go through the roof. -- chris Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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