Can java.lang.StringBuffer be replaced by the "regular" string manipulation logic in ColdFusion?

Question

I am not an expert in Java; I am hoping that someone on this list who are more proficient in Java can help me out.

I have the following codes on my current server.

<cfset var buffer = CreateObject("java", "java.lang.StringBuffer").init("") />
<cfset buffer.append(variables.myVar) />

I am trying to move these codes to another server. The problem is that this new server (shared hosting) does not allow invoking of a Java Object. So, I changed them to the followings.

<cfset var buffer = "" />
<cfset var buffer = buffer & variables.myVar />

My question is, are the new codes equivalent to the old ones? What are the advantages of using java.lang.StringBuffer?

Thanks in advance, Monte

Is there any reason to use StringBuffer instead of StringBuilder? — Peter Lawrey, Jun 06 '11 at 17:14
If synchronization were a concern, you would probably want StringBuffer. Though it might just be old code. IIRC, StringBuilder was not added until jvm 1.5. — Leigh, Jun 06 '11 at 18:26
Peter, the codes using StringBuffer were done by somebody else. — Monte Chan, Jun 06 '11 at 20:12

Tomalak · Accepted Answer · 2011-06-06T18:51:01.183

6

No, the "new" code is less efficient when used in a heavy loop.

You can emulate StringBuffer with an array.

<cfset var buffer = ArrayNew(1)>
<cfset ArrayAppend(buffer, variables.myVar1)>
<cfset ArrayAppend(buffer, variables.myVar2)>
<!--- more of these --->
<cfset result = ArrayToList(buffer, "")>

However: If you are not concatenating hundreds or thousands of strings in a row, there is little benefit in using StringBuffer. You can go with & in most cases.

I have done some testing (on a ColdFusion 7 server w/ Java 1.4, more recent editions might score differently).

All times are milli-seconds The results are averaged over 10 repeats (except the one in square brackets as this took virtually forever).

The following is the measurement of iteratively concatenating a single letter N times.

iterations   concat   array   cfsave   string
                             content   buffer
       100        0       0        0        2
      1000        4       4        2       22
     10000      168      29       33      219
    100000   30,781     168      293    1,575

The following is the result of iteratively concatenating a string of length 10 N times:

iterations   concat   array   cfsave   string
                             content   buffer
       100        0       0        0        4
      1000       25       0        2       24
     10000    1,242      33       31      232
    100000 [410,979]    180      373    2,082

Note how basic string concatenation gets rapidly more inefficient the more iterations you do and the longer the string gets. The other methods show more linar behavior.

Further notice that the StringBuffer's performance is also tied to its initial size. If you dimension it too small (i.e. by calling init("") instead of .init(10000), for example) then it is forced to re-allocate more space when it runs out, which also takes time. For the sake of test, I initialized it with exactly the amount of space it would need.

edited Jun 06 '11 at 18:51

answered Jun 06 '11 at 15:40

Tomalak

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Assuming Adobe's implementation of ArrayToList() is efficient? – Henry Jun 06 '11 at 16:51
@Henry: It will call `join()` on the underlying array. – Tomalak Jun 06 '11 at 16:53
1

@Tomalak `join()` in Java? I only heard of Array.join in JavaScript... Unless CF uses `org.apache.commons.lang.StringUtils`? – Henry Jun 06 '11 at 16:56
1

@Henry: Hm. I simply assumed it was there (I mean, there is `split()` on strings…). Stupid me. :-\ – Tomalak Jun 06 '11 at 17:05
see my updated answer, the solution you purposed is actually the fastest! – Henry Jun 06 '11 at 17:12
@Henry: Thanks for testing this! :) I'm performance-testing myself right now, as you seeded some doubt in me. – Tomalak Jun 06 '11 at 17:14
@Tomalak I didn't test it myself, it was done by CFInsider's Jason Delmore :) – Henry Jun 06 '11 at 17:22
1

@Henry Now I did some proper testing myself. See modified answer. – Tomalak Jun 06 '11 at 18:34
@Tomalak Thought you'd be using `StringBuilder` – Henry Jun 06 '11 at 18:38
@Henry I just noticed that the server runs Java 1.4, so that was not an option. I tried 1.5 a while ago but I guess it was not too stable so I rolled it back and forgot about it. ;-) – Tomalak Jun 06 '11 at 18:47
@Tomalak still doing CF7? Time to upgrade. :) – Henry Jun 06 '11 at 18:59
@Henry: Not me to decide. ;-) But, yes, we will upgrade soon. – Tomalak Jun 06 '11 at 19:00
1

That's very thorough. Thank you for showing the performance data. – Monte Chan Jun 06 '11 at 20:09

score 2 · Answer 2 · answered Jun 06 '11 at 15:48

Technically, no. But practically, I think it is fine.

StringBuffer is a mutable object, hence the reason you are able to append(). ColdFusion strings, like Java Strings) are immutable, so you need to create a new string and overwrite the old (which is what you are doing in the above example).

I am not sure, but you might see a minor (milliseconds) performance different, and you are, technically, creating more objects with the ColdFusion method, but since you are using shared hosting you probably don't really care about that kind of performance difference anyway.

Unless you are doing hundreds or more of these, I doubt you will notice a difference.

JIT compiler would be smart enough to optimize the basic string append "+=" into using StringBuffer if and when it sees fit, but not sure about CF's "&=". See: http://stackoverflow.com/questions/599161/best-way-to-convert-an-arraylist-to-a-string — Henry, Jun 06 '11 at 16:48

Henry · Answer 3 · 2011-06-06T17:20:59.930

Use <cfloop> inside <cfsavecontent>. If what you're constructing is space-sensitive, please double the output for extra space/newline, and code your <cfloop> and <cfsavecontent> accordingly (i.e. in one line).

I've come cross tests that have shown that it is even faster then Java's StringBuilder.

Update: http://www.cfinsider.com/index.cfm/2009/10/23/High-Performance-String-Concatenation-in-ColdFusion

from fastest to slowest:

ArrayAppend() and then ArrayToList()
<cfsavecontent>
StringBuilder's append()
basic string concat using &

Can java.lang.StringBuffer be replaced by the "regular" string manipulation logic in ColdFusion?

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