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Java Forum / General / November 2006'dynamic arrays' in java
i am writing a java method which needs to take note of a set of numbers generated by the routine as it runs. the problem is that i dont know beforhand how many of these numbers will be generated, so the simple use of an array cant be used as java seems to insist of the size of the array to be declared upfront, where as i say i dont have this information prior to running the method. there are other java data constructs but i am a bit bemused as to what would be appropriate here. i am no java expert so what i am looking for is what used (or still is i dont know) to be called a 'dynamic array' ie. one whose size may change throughout the running of a program thanks >i am writing a java method which needs to take note of a set of numbers > generated by the routine as it runs. the problem is that i dont know [quoted text clipped - 11 lines] > whose > size may change throughout the running of a program java.util.ArrayList Matt Humphrey matth@ivizNOSPAM.com http://www.iviz.com/ >> i am writing a java method which needs to take note of a set of numbers >> generated by the routine as it runs. the problem is that i dont know [quoted text clipped - 13 lines] > > java.util.ArrayList If numbers are ints and they are later used for lookups (rather than iterating) a BitSet may also serve well here. Kind regards robert > i am writing a java method which needs to take note of a set of numbers > generated by the routine as it runs. the problem is that i dont know [quoted text clipped - 8 lines] > used (or still is i dont know) to be called a 'dynamic array' ie. one > whose size may change throughout the running of a program You're looking for a Vector.  Signaturesimon@jasmine.org.uk (Simon Brooke) http://www.jasmine.org.uk/~simon/ ;; Conservatives are not necessarily stupid, ;; but most stupid people are conservatives -- J S Mill > > i am writing a java method which needs to take note of a set of numbers > > generated by the routine as it runs. the problem is that i dont know [quoted text clipped - 10 lines] > > You're looking for a Vector. I doubt he's looking for a Vector, ArrayList is much more appropriate in most circumstances. > -- > simon@jasmine.org.uk (Simon Brooke) http://www.jasmine.org.uk/~simon/ > > ;; Conservatives are not necessarily stupid, > ;; but most stupid people are conservatives -- J S Mill >> You're looking for a Vector. > I doubt he's looking for a Vector, ArrayList is much more appropriate in > most circumstances. Always declare using the List interface, that way you can easily change the actual implementation to see which gives you the best performance. HTH, La`ie Techie > i am writing a java method which needs to take note of a set of numbers > generated by the routine as it runs. the problem is that i dont know [quoted text clipped - 9 lines] > > thanks Use ArrayList instead. Signaturetrippy mhm31x9 Smeeter#29 WSD#30 sTaRShInE_mOOnBeAm aT HoTmAil dOt CoM NP: "All I Really Want" -- Alanis Morissette "Now, technology's getting better all the time and that's fine, but most of the time all you need is a stick of gum, a pocketknife, and a smile." -- Robert Redford "Spy Game" > i am writing a java method which needs to take note of a set of numbers > generated by the routine as it runs. the problem is that i dont know [quoted text clipped - 7 lines] > used (or still is i dont know) to be called a 'dynamic array' ie. one whose > size may change throughout the running of a program The closest to dynamic array is ArrayList, an array based implementation of the java.util.List interface. However, in the first sentence you mention a "set of numbers". If the only reason for associating an order with them is because you were thinking of putting them in an array, then consider a java.util.Set implementation instead. In particular, if you frequently ask "Is n in the result set?" then a HashSet may be more efficient and appropriate than any List implementation. If the numbers are reasonably small, BitSet may also be a good choice. If you have not already done so, take a look at the API documents for java.util. It has a lot of classes for solving "how do I store this data?" questions. Patricia 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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