throw an exception in code

[JosAH]

That piece of code doesn't make sense at all. If you want to define your own
Exception you just extend from the Exception class or the RuntimeExceptio n
class which both extend from the Throwable class. Check the API documents
for those classes and please don't try to guess what the syntax would or should
be for the Java language. My guess is that you either forgot a lot about Java or
you haven't studied Java much at all before.

kind regards,

Jos

[Dlangdaman]

I am 100% a novice and never claimed to know fully what Im doing. to politely put me down will not improve the issue now will it?

[JosAH]

I am 100% a novice and never claimed to know fully what Im doing. to politely put me down will not improve the issue now will it?

That fully contradicts your very first sentence in your original post:

Its been a while since I have had Java

My advice remains the same: read Sun's Java tutorials first and don't just guess
what the syntax and semantics of Java should or would be according to you.

kind regards,

Jos

[Dlangdaman]

Im trying this and getting Grades.java:39: reached end of file while parsing which I have no idea what that means....thanks again

throw new exception(InvalidGradeException);
                    
        }
        for(i = 0;i < grades.length; ++i)
            
        {
            sum += grades[i];
        }
        ave = sum / 5.0f;
        sResult = "The Class average is " + Float.toString(ave);
        JOptionPane.showMessageDialog(null,sResult);
   } 
    public static void main(String args[])
    {
        new Grades();
        System.exit(0);
    } 
    class InvalidGradeException extends NumberFormatException {
    public InvalidGradeException(String s) {
        super(s);
    }

[Dlangdaman]

my first statement says it has been a while since I had JAVA...meaning a class about a year ago with no practice...so that makes me a NOVICE....i am trying to pick this stuff up without guess I just have issues with the formating and use of some items...i am much better with VB

[r035198x]

Im trying this and getting Grades.java:39: reached end of file while parsing which I have no idea what that means....thanks again

throw new exception(InvalidGradeException);
                    
        }
        for(i = 0;i < grades.length; ++i)
            
        {
            sum += grades[i];
        }
        ave = sum / 5.0f;
        sResult = "The Class average is " + Float.toString(ave);
        JOptionPane.showMessageDialog(null,sResult);
   } 
    public static void main(String args[])
    {
        new Grades();
        System.exit(0);
    } 
    class InvalidGradeException extends NumberFormatException {
    public InvalidGradeException(String s) {
        super(s);
    }

From that tutorial link that I gave you, what did they say was the syntax for throwing an Exception? I've already given you the exception class which you really should have written on your own.

[Dlangdaman]

im not sure why everyone is so hostile to help...writing that little bit of code helped me out alot and didnt hurt anyone...i am just trying to improve this app and learn at the same time...Thanks guys

[r035198x]

im not sure why everyone is so hostile to help...writing that little bit of code helped me out alot and didnt hurt anyone...i am just trying to improve this app and learn at the same time...Thanks guys

No one is trying to be hostile. We are trying to make sure that you learn this the correct way.
There's no point in just giving you all the working code without understanding it.

[Dlangdaman]

i agree...but to show me the working code and where it goes...would give me a working example that I can further develop off of and learn from...at least thats the best way I learn.....Thank s again

[JosAH]

i agree...but to show me the working code and where it goes...would give me a working example that I can further develop off of and learn from...at least thats the best way I learn.....Thank s again

You could copy and paste working code and it probably keeps on working while
you would have no idea *why* and *how* it works. We're here to make people
understand *why* things work and *how* they work; not *that* they work because
we already knew that but you didn't. It has nothing to do with hostility.

kind regards,

Jos

[Dlangdaman]

This Runs and kills the app when you put in an invalid number
But What I want is for it to stop and tell the user and then they can continue...how would I do that?
can you explain the " SUPER(S)" at the end?

import javax.swing.JOptionPane;
 
public class Grades
{
       
   public Grades()
    {
        float grades [] = new float[5];
        float ave, sum = 0.0f;
        String students[] = {"Tim", "Mary", "Jen","Derek", "John"};
        String sgrades, sResult;
        
        int i;
        for(i = 0; i < grades.length; ++i)
        {
            sgrades = JOptionPane.showInputDialog(null,
                    "Enter the Student's Grade: ", students[i],1);
                    grades[i] = Float.parseFloat(sgrades);
                    if(grades[i] > 100 || grades[i] < 0)
                    throw new InvalidGradeException("Invalid grade.");
                    
        }
        for(i = 0;i < grades.length; ++i)
            
        {
            sum += grades[i];
        }
        ave = sum / 5.0f;
        sResult = "The Class average is " + Float.toString(ave);
        JOptionPane.showMessageDialog(null,sResult);
   }
    public static void main(String args[])
    {
        new Grades();
        System.exit(0);
    }
   class InvalidGradeException extends NumberFormatException {
    public InvalidGradeException(String s) {
        super(s);
    }
 
}
}

[JosAH]

This Runs and kills the app when you put in an invalid number
But What I want is for it to stop and tell the user and then they can continue...how would I do that?
can you explain the " SUPER(S)" at the end?

An Exception carries a message and an optional 'cause' around. The 'cause'
can be another Exception which is wrapped in the Exception being thrown.
The 'cause' doesn't apply to your Exception but the message does: the 'super(s)'
call simply sets the 'message' member to 's'.

A Exception being thrown simply aborts the normal flow of execution. If you don't
catch it you're 'dead'. If one illegal number entered by the user causes an Exception
to be thrown by your own code, you should catch it and do something about it.
Please do read the tutorials. The link to the relevant tutorial was supplied to you
in a previous reply already.

kind regards,

Jos

[Dlangdaman]

can you lead me through setting up an exception that give a GUI ok or cancel and then lets them proceed with entering? i have it throwing an exception now but it just kills the program

[r035198x]

can you lead me through setting up an exception that give a GUI ok or cancel and then lets them proceed with entering? i have it throwing an exception now but it just kills the program

Let's see what you have then

[JosAH]

can you lead me through setting up an exception that give a GUI ok or cancel and then lets them proceed with entering? i have it throwing an exception now but it just kills the program

That's because you don't catch that exception anywere. An uncought exception
finally lands at the outmost level, i.e. the jvm itself, which reports the exception
and just terminates because the jvm doesn't know what to do with the exception,
i.e. it doesn't know how to handle it.

Basically your code should look like this:

[code=java]
try {
// your code here that can throw exception X
}
catch(X x) {
// your code did throw exception X; handle it here
}
[/code]

kind regards,

Jos