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Check for non-numeric value

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blinton25

blinton25

Programmer
Mar 20, 2004
104
BB
Hi,

I have the following code:


<HTML>
<HEAD>
<TITLE>Project 4-1</TITLE>
</HEAD>
<BODY>
<% String amount = request.getParameter("sales");
if(amount == null) amount = "0";
int sales = Integer.parseInt(amount);

double comis = 0; //commission stored here
double total = 0;

%>
<b>Enter the amount of your sales:</b>
<form name="thisForm" action="Project1.jsp" method=post>
Amount of sales:<input name=sales size=10>
<input type=submit value="Get commissions">
</form>

<% if (sales>=1 && sales<=2000) {
comis = (sales*0.03);
total = (comis+sales);

} else if (sales>=2001 && sales<=5000) {
comis = (sales*0.04);
total = (comis+sales);

} else if (sales>=5001 && sales<=7000) {
comis = (sales*0.07);
total = (comis+sales);
} else if (sales>=7001) {
comis = (sales*0.10);
total = (comis+sales);
}%>

<% out.print("Sales is "+sales+" Commission is "+comis+" Total is " + total);
%>

</BODY>
</HTML>

It works ok but if I don't enter a value or enter a non numeric value in the sales field I receive an error.

How can I check if nothing or a non-numeric value is entered. I would rather not do it as a try-catch though.
 
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Hi

Check it with regular expression, using [tt]String.matches()[/tt].
Code: 
[gray]// ...[/gray]

String amount = request.getParameter("sales");

[highlight #eee]if (amount.matches("\\D")) System.out.println("Invalid character");[/highlight]

if(amount == null) amount = "0";
int sales = Integer.parseInt(amount);

[gray]// ...[/gray]

Feherke.
 
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Integer.parseInt throws an Exception if a non number argument is received: you can catch that exception.

Cheers,
Dian
 
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I would rather not do it as a try-catch though. "

Thanks
 
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The persons that I am demonstrating this to have not been through this as yet.
 
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Ah. You're a trainer, then? Have they 'been through' regular expressions yet? :)

Tim
 
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Hi

Christiaan said:
That will loose you some students.
Click to expand...
Why ? Just because you, as Windows fan, are not familiar with regular expressions ?

I knew regular expressions couple of years before Java. When I read about them in the API, first I thought it is just cheap replacement. And when I saw that Java can handle almost Perl compatible regular expressions, I was impressed. For me the flexibility of the implemented regular expressions is a good consolation for the rigidity of the language, especially the imposed exception handling.

Feherke.
 
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I've been a trainer for a long time, and I'd never start teaching Java with regular expressions.

Exception is a key concept not for Java but for programming so it's clearly something they need to know.

Maybe regular expressions are nice for a Perl programmer, but I think they're a programming language themselves.

Cheers,
Dian
 
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Hi

Of course, you do not begin with regular expressions. They are not the first step neither in Perl.

But if you would, I do not believe that you would loose students.

Feherke.
 
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Well, I guess it depends on the audience and the objectives of training, but for Java novice, I'd rather tell them to do it with Integer.parseInt or Character.isDigit.

Cheers,
Dian
 
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Who says I'm a windows fan. I use linux (kubuntu) and Java at home. I just have to use vb.net at work (well I don't have to but it would take to much time to convert the current projects).

I just think you would loose more students if you have regex before exceptions instead of the other way round. And believe me you already loose a lot of students no matter what.

I'm in my final year (I hope) of an associates degree (in eveningschool) and we started with 60 3 years ago and are now left with 3. All programming is done in Java. So we get a chance to go into one language. And I'm pretty sure that we would be 2 if regex came before exceptions. I think regex is a nice addition to any programming language but not a must (you can probably do the same without them albeit a bit slower most of the time) while excpetions are a must.

Christiaan Baes
Belgium

"My new site" - Me
 
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I just don't think this site has the right/big enough userbase for linux/java. And I mostly find my answers after a google or a lot of hard work and swearing.

Christiaan Baes
Belgium

"My new site" - Me
 
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chrissie said:
And I mostly find my answers after a google or a lot of hard work and swearing
Click to expand...

... ah, it's not just me then? [wink]

Tim
 
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