Struts has many dependencies already and I'd like to avoid adding one with lang. Why not just size a large StringBuffer and trade memory for speed?
David --- Martin Cooper <[EMAIL PROTECTED]> wrote: > Rather than add a new string utility class to Struts, which isn't really > where it should belong, I think we'd be better off just using this: > > http://jakarta.apache.org/commons/lang/api/org/apache/commons/lang/StringUti > ls.html#join(java.lang.Object[]) > > Alternatively, you could suggest (on the commons-dev list) adding a > variation of your StringHolder class, based on the join() method above, > to > Commons Lang. > > -- > Martin Cooper > > > > -----Original Message----- > > From: nishant kumar [mailto:[EMAIL PROTECTED] > > Sent: Saturday, February 14, 2004 5:46 PM > > To: [EMAIL PROTECTED] > > Subject: string concatenation > > > > > > hi, > > I have a performance tuning suggestion which i think will greatly > > impact the performance of struts html tags. > > String concatenation using StringBuffer is definitely much > > better than > > using the plus operator but there are scenarios where there are much > > better ways than using StringBuffers. Actually struts html tags fall > in > > those scenarios. > > So let me give you an example. this is the code from > > renderFormStartElement method of FormTag. > > > > StringBuffer results = new StringBuffer(); > > results.append("<form"); > > results.append(" name=\""); > > results.append(beanName); > > results.append("\""); > > results.append(" method=\""); > > results.append(method == null ? "post" : method); > > results.append("\" action=\""); > > .... > > str = results.toString(); > > > > pageContext.getOut().write(str); > > > > Now lets list the issues with this. > > 1. first presizing this buffer is quite difficult (avoided in this > > case). here the buffer starts with size 16 and doubles each time the > > size is exceeded. This causes unnecessary creation of new char arrays > > and redundant copy of data whenever resizing happens. > > 2. whenever append is called data is copied from the passed string to > > the end of stringbuffer. > > 3. finally the whole concatenated data is again copied into another > > string. > > 4. and then in the end this string is written to a writer, another > copy, > > which is the only copy required. > > > > so even if you had presized the stringbuffer correctly, you have > copied > > the same data thrice instead of just once. And you also create two NOT > > needed objects. > > > > so here is the solution i propose. have a class holding an array of > > Strings and keep appending strings to this array and finally print > this > > array to the writer. something like this. > > > > private String[] data = new String[256]; > > private int size = 0; > > > > public StringHolder append(String str){ > > ensureCapacity(this.size + 1); > > this.data[this.size++] = str; > > return this; > > } > > > > public void writeTo(Writer out) throws IOException{ > > for (int i = 0; i < this.size; i++){ > > if (this.data[i] != null){ > > out.write(this.data[i]); > > } > > } > > } > > > > this way only the last copy takes place and you also avoid creating so > > much garbage. > > > > i have attached StringHolder class which does the above task and also > > the FormTag after making necessary modification to fit in this class. > > >From the code of FormTag you can see that you need to make quite few > > changes to get great benefit. > > > > i have also attached a better implementation of > > ResponseUtils.filter(String) method. the logic is on the same lines as > > above. > > > > thanks, > > nishant > > > > -- > > nishant kumar <[EMAIL PROTECTED]> > > > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > __________________________________ Do you Yahoo!? Yahoo! Finance: Get your refund fast by filing online. http://taxes.yahoo.com/filing.html --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
