You are right, Gwt is optimized to perform the best in each case.
Both StringBuilder and StringBuffer generates the same javascript code.
I have coded a simple test (see below) to check append and these are
my results (Compiled code):
- all browsers except IE performs identical using String, StringB.
- IE6 performs better using StringB.
- IE8 performs better using normal String.
In hosted mode, the performance is better for StringB
Cheers
-Manolo
public void testStringOperations() {
int TIME = 20000;
String DATA = "sadfasdf";
String s = "";
double ss = new Date().getTime();
for (int i=0; i<TIME; i++) {
s += DATA;
}
double se = new Date().getTime();
String a = "";
double as = new Date().getTime();
for (int i=0; i<TIME; i++) {
a = a + DATA;
}
double ae = new Date().getTime();
double bs = new Date().getTime();
StringBuffer b = new StringBuffer();
for (int i=0; i<TIME; i++) {
b.append(DATA);
}
double be = new Date().getTime();
double us = new Date().getTime();
StringBuilder u = new StringBuilder();
for (int i=0; i<TIME; i++) {
u.append(DATA);
}
double ue = new Date().getTime();
RootPanel.get().add(new Label(se - ss + " " + s.length() + " String += "));
RootPanel.get().add(new Label(ae - as + " " + a.length() + "
String = String + "));
RootPanel.get().add(new Label(be - bs + " " + b.length() + "
StringBuffer" ));
RootPanel.get().add(new Label(ue - us + " " + u.length() + "
StringBuilder" ));
}
On Tue, Jul 13, 2010 at 11:41 AM, Thomas Broyer <t.bro...@gmail.com> wrote:
>
>
> On 13 juil, 11:10, Manuel Carrasco Moñino <man...@apache.org> wrote:
>> I've not checked the code produced by the Gwt compiler, but I think it
>> could introduce a bit of overhead or may be none (if the
>> implementation code was 100% optimal).
>> Anyway the use of String should guarantee that the final code is
>> faster or equal.
>
> That's wrong. StringBuilder will use either string concatenation (in
> which case you'll suffer a very small, and negligible, penalty at
> runtime) or array-append-then-join, depending on which method was
> benchmarked the fastest in each browser.
> http://code.google.com/p/google-web-toolkit/source/browse/trunk/user/super/com/google/gwt/emul/EmulationWithUserAgent.gwt.xml
> The GWT has experimented with many options before settling on these
> two: using a.push() or a[arrayLength++] to append to an array, using
> join() or String.prototype.concat.apply() to join the array items into
> a string, etc. you'll find them all in the subversion repository:
> http://code.google.com/p/google-web-toolkit/source/browse/trunk/user/src/com/google/gwt/core/client/impl/
> Note that string concatenation is done using the += operator, which is
> more performant than s = s + something in some browsers (AFAIK).
>
> So really, GWT is optimized here, and you shouldn't fear from using
> StringBuilder (or StringBuffer) if you think they're necessary (of
> course, when concatenating 3 strings, it might not be worth it;
> StringBuilder is mostly useful with loops and/or building large
> strings, and this is true in both Java and GWT)
>
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