How can I make this code faster? optimized.

Question

Its part of two jsp pages that go back and forth. I feel I am creating new strings all of the time. I have 3 graphic representations of a radion button and a check box. its for a quiz program.
if the button is not checked, it uses rd0.gif.
if the button is checked, then its assigned rd1.gif.
However, if the button is the wrong answer, then its assigned rd2.gif.
the use of char arrays is neccasary, but not vital, I guess I could use indexof in the string. But I Dont know if its faster. I want to optimize the code, so it uses less resources.
heres the code
TrueFalse=entry[11].indexOf("TRUE");
myButton = Integer.parseInt((String)session.getAttribute("BUTTONNO"));
GivenAnswer =(String)session.getAttribute("GIVEN");
if(TrueFalse==-1) {
char[] questions = GivenAnswer.toCharArray();
for(x=1;x<5;x++) {
if(questions[x]=='1') { bp[x]="images/ck1.gif"; }else{ bp[x]="images/ck0.gif";}
}else{
if(myButton==1) {bp[1] = "images/rd1.gif";} else {bp[1] = "images/rd0.gif";}
if(myButton==2) {bp[2] = "images/rd1.gif";} else {bp[2] = "images/rd0.gif";}
questions is discarded.
the quiz is fast at the begining, but once you go deeper and deeper it slows down. This is the second page:
<%@ include file ="include4.jsp" %>
<%
session.setAttribute("BUTTONNO", "1");
GivenAnswer =(String)session.getAttribute("GIVEN");
char[] questions = GivenAnswer.toCharArray();
questions[1]='1';
tempString = new String (questions);
GivenAnswer = tempString;
session.setAttribute("GIVEN", GivenAnswer);
%>
<jsp:forward page="train2.jsp">
</jsp:forward>
I tried to keep all of the code on one page, but I am using images instead of real radio buttons, for several reasons. JSP doesnt seem to return a value for check/radio buttons in JSP, so clicking on an anchored image and going to a second JSP PAge seemed reasonable. I dont know how to force garbage collection. But the speed in which the pages and images appear, get slower and slower. so I Think im using up memory (Stings) at a greater rate than I should.
thanks
MIKe NIEMI
[email protected]

Answer 1

I'm not sure that an "optimisation" is necessarily what you're after. I doubt it's the creation of Strings that's causing any performance issue - even if it is then it's probably the result of something more sinister.
Don't assume that your code is using a lot of resources.
For example it's tempting to change it to this:
if(myButton==1) {bp[1] = "images/rd1.gif";} else {bp[1] = "images/rd0.gif";}
if(myButton==2) {bp[2] = "images/rd1.gif";} else {bp[2] = "images/rd0.gif";}
// change to this?
bp[myButton] = "images/rd1.gif";
bp[3 - myButton] = "images/rd0.gif";I'd say that the original code was clearer and used just as many resources (once the Strings are interned).
The same goes for this:
if(questions[x]=='1') { bp[x]="images/ck1.gif"; }else{ bp[x]="images/ck0.gif";}
// change to this?
bp[x] = "images/ck" + questions[x] + ".gif";Again, the former is possibly clearer as it indicates that questions is really a boolean flag - it should also be easily optimised by the compiler.
You're right that you could replace "questions" by simply using GivenAnswer.charAt(x).
Enterprise Java applications can generate hundreds of thousands of Strings during their execution - your Servlet is unlikely to have a serious impact on that unless you've got an enormous loop in there or a very large user base.
A golden rule of optimisation is not to assume that you know where the performance/resource bottlenecks are. Measure the improvement you get from a change - does it warrant the resultant increase in the complexity of the code?
Put some profiling in your code - how long is it taking to run your Servlet? How many times is it being invoked? I can't imagine that the code you've provided will take more than a few milliseconds to run.
Also, you can't force garbage collection. You can suggest it to the Java runtime (it might not even have a garbage collector!). However, this generally indicates a flaw in the application and should be avoided unless absolutely necessary (and it's not in this case!).
If you really want to optimise then get hold of something like OptimizeIt - it will provide a great deal of information about what's being created and where.
Hope this helps.