asked on

convert string to float

hello ,
i want to get float from session .
this is my code .

i put the string in the session here :

session.setAttribute("solde",rs.getString("solde"));

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then i want to get it like a float from the sesison . Can u help me please

Mick Barry

float f = Float.parseFloat(session.getAttribute("solde"));

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for_yan

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SOLUTION

Mick Barry

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keviin555

ASKER

float f = Float.parseFloat(session.getAttribute("solde"));

it don't work :/

@for_yan

i dont understand :/ and i dont use jsp , i use servlet .

for_yan

you should not use parseFloat
you shoul rahte use methiod

..floatValue()

for_yan

Float.parseFloat(s) requires String argument

if your caase (Float) session.getAttribute("solde") returns you Float value
to get float from it you use method floatVlaue

float f = ( (Float) session.getAttribute("solde") ).floatValue()

keviin555

ASKER

with this
float f = ( (Float) session.getAttribute("solde") ).floatValue()
i have error 500 , null pointer exeption .

if your caase (Float) session.getAttribute("solde") returns you Float value

i think it return a String

for_yan

Did it retrivee anything elase form this session?
Myabe it didn't retriev session? Id session is null,
Then session.getAtribute whill give null pointer excpetion

Are you sure this part
session.setAttribute("solde",new Float(rs.getString("solde")));
worked?

for_yan

Maybe session could have timed out, if you waited too long?

I usually do such check:

HttpSession sess = req.getSession(false);
if(sess == null) {
out.println("<html><head><title>Session expired</title></head>");
out.println("<body><h1>Session expired. Start with the Review screen</h1><BR></body></html>");
return;
}

keviin555

ASKER

i forgot this part
session.setAttribute("solde",new Float(rs.getString("solde")));

:)

thank you

for_yan

Yes, pretty important part :)

for_yan

objects will be unhappy; in all justice this should rather be split

keviin555

ASKER

ah ok .

and when i want to do this :

String m = req.getParameter("solde");

and then convert m to float ?

for_yan

No, req.getParameter(..) returns String
after that you can use that

float f = Float.parseFloat(m);

for_yan

However the good practice is ffirst to check if this string m
can be converted to float

Say,

boolean goodNumber = true;

try{

new Float(m);

}
catch {
goodNumber = false;
}

if(!goodNumber) {out.prinltn("error in input");
//and end here because you cannot go further
}

float f = Float.parseFloat(m);

for_yan

Becuase often thsi string comes from user's input in the form, and who knows
waht user could have enetered there

keviin555

ASKER

ok thank you very much . But i have a problem with the firs float . There is a difference between (Float and float ) ?

i have
String m = req.getParameter("montant");
float mont = Float.parseFloat(m);

and this
session.setAttribute("solde",new Float(rs.getString("solde")));
f = ( (Float) session.getAttribute("solde") ).floatValue();

i want to make :

if (f>m)
{
f-=m;
}

but it dont work

for_yan

float - is primitive reprsenting float number

Float - is object - wrapper around the float primitive
Float is not the same as float, you cannot add two Float objects,
you cannot multiply them, etc
float number is just a field of the Float object.
therefore sya floatValue() is a method of Object Float which exposes
this primitive field; new Float(float f) creates object with the primitive field eqqual to f.
Float.parseFloat(String s) - static method of the Float class - kind of convenience
method which goes into details nanlyses all characters of string and figures out
if these characters make up something that may reoresent float primitive number
and returns this number, or, alternaticvely, throws exception indicating that this String is no
good for making up a float number
Static method has nothing to do with any particular Float isnstance

method req.getParameter("name")
always returns String, that String may either represent a number, or a text or anything,
but at the moment when you get it
m = req.getParameter("name"), m is just a String

Therefore if(f>m) makes no sense, f is float, m is String
What you can do is to analyze what kind of Struing is m (see my previous post)
and maybe ity is inded can be converted to number

for_yan

then you can make

float f1 = Float.parseFlaot(m);
and then you can compare
f and f1
if(f>f1) will be valide syntax

CEHJ

>>float f = Float.parseFloat(session.getAttribute("solde"));

Won't work. Session returns Object. You need

float f = Float.valueOf((String)session.getAttribute("solde"));

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for_yan

I think this would be fair to split 250/250 between http:#35734130 and http:#35734174