Thread: Prime number problem (please help)

Originally Posted by Norm

Please post the whole class where that statement is.

The error message says that statement is in the wrong place in the code.

Do you know how to define a variable?

i posted the entire program a while ago. See post #20.

a variable is a temporary data store. it is defined using a specified data type for example int,double,char,string followed by the variable name.
for example int num;

I dont understand what you are telling me to do. My tutor said he is not teaching files but will be tested on it.
Can anyone on this forum help me please?!

Originally Posted by Norm

It has a problem and needs to be changed. That is what all the posts since then have been about. You were supposed to change the code.

Move the definition for the variable: out outside of the main() method so it is a class instance variable, NOT a variable that is locally defined in the main() method. Then all the methods in the class will be able to use it.

Do some research on what the scope of a variable means.

man this is not working. i did what u just said and this is what i get

--------------------Configuration: <Default>--------------------
C:\Users\DesktopPrimes.java:13: error: non-static variable out cannot be referenced from a static context
out.close();
^
C:\Users\DesktopPrimes.java:26: error: non-static variable out cannot be referenced from a static context
out.printf(i);
^
C:\Users\DesktopPrimes.java:26: error: no suitable method found for printf(int)
out.printf(i);
^
method PrintWriter.printf(Locale,String,Object...) is not applicable
(actual argument int cannot be converted to Locale by method invocation conversion)
method PrintWriter.printf(String,Object...) is not applicable
(actual argument int cannot be converted to String by method invocation conversion)
3 errors

Process completed.

Originally Posted by Norm

Too much code in static methods is causing that error.
Did you Google that error. It is very common.

For now make out a static variable.

what variable do i make a static variable for???

The error says:

C:\Users\DesktopPrimes.java:13: error: non-static variable out cannot be referenced from a static context
out.close();
^

Notice there's a little caret that even points at it for you.

Also notice that your last error indicates that there is no method printf( int ) for the variable out.

Originally Posted by GregBrannon

The error says:

C:\Users\DesktopPrimes.java:13: error: non-static variable out cannot be referenced from a static context
out.close();
^

Notice there's a little caret that even points at it for you.

Also notice that your last error indicates that there is no method printf( int ) for the variable out.

ok i solved the printf(int) error. Now how do i fix the out.printf???

Originally Posted by Norm

Is this the one?

Change printf() to print()
Or read the API doc for the printf() method to see how to use it.

If you have questions about the API doc, copy the doc here and ask your questions about the part you are confused about.

i did that but now im stil getting the same error at the out.close() and out.print.

this is the error:error: non-static variable out cannot be referenced from a static context

i googled it but i dot understand what to do.

this is due today

Originally Posted by Norm

Make out a static variable.

ok but what variable do i use for that?

Originally Posted by Norm

??? I just said the name of the variable that should be made static: out

See the tutorial about static: Variables (The Java™ Tutorials > Learning the Java Language > Language Basics)

can u just tell me how to do it?
i dont understand what you are saying.
out is used as my file pointer for the output file.

PrintWriter out = new PrintWriter(new FileWriter("output.txt"));
how do i fix this?

Originally Posted by Norm

Put the keyword static first thing on the line.

Static PrintWriter out = new PrintWriter(new FileWriter("output.txt"));

is that it?

Originally Posted by Norm

Did you try changing the source and compiling it? What did the compiler say?

I dont know what you mean by changing the source. I tried using the static thing like you said but its giving an error saying cannot be dereferenced.

So i took out the static thing altogether. What i did is moved the PrintWriter out statement and the out.close() statement to the Sieve method and it works perfectly now. The primes are outputted to a file.

Although i did not understand too much of what u said I guess it helped a bit. So thanks!