Exceptons

[Shananne DuFrame]

I am having difficulties getting this to throw an exception for negative numbers. I've gotten it as far as stating length cannot be negative but it continues to convert to centimeters. example:


Enter the length in feet and inches seperated by a space: -5 4

Exception: Length cannot be negative.
The total length converted to centimeters is: -142.24

I tried doing, but didn't work!!

if (feet<=0)
  negMethod(); 
   
//method to trow negatives
public static void negMethod() throws Exception
{
   throw new Exception("Exception: Cannot use a negative number.");
}

Here's my code:

import java.util.*;
 
public class CentimetersExceptionHandling
{
static Scanner console = new Scanner (System.in);

public static void main(String[] args)
{
double feet;
double feetToInches=0;
double totalInches;
double inches;
double centimeters;
boolean done;
String str, strneg;

done = false;

do
{
try
{ 
System.out.print("Enter the length in feet and inches seperated by a space: ");
feet = console.nextDouble();
inches = console.nextDouble();
System.out.println();

if (feet<=0)
System.out.println ("Exception: Length cannot be negative." );

feetToInches = feet*12;
totalInches = inches + feetToInches;
centimeters = 2.54*totalInches;
done = true;

System.out.println("The total length converted to centimeters is: " + centimeters);
}
 
catch (Exception imeRef)
{
str = console.next();

System.out.println("Exception " + imeRef.toString() + " " + str);
}
}
while (!done);
}
}

    

[Ta Ri Ki Sun]

Your problem is in the do while loop, you're never "done".

Replace

  if (feet<=0)
                System.out.println ("Exception: Length cannot be negative." );  

with

    if (feet<=0)
          {
            done = true;
            throw new IllegalArgumentException("Exception: Length cannot be negative." ); 
          }  

[ November 28, 2006: Message edited by: Ta Ri Ki Sun ]

[Shananne DuFrame]

After doing as said the results are:

Enter the length in feet and inches seperated by a space:
1 2

The total length converted to centimeters is: 35.56

----jGRASP: operation complete.

----jGRASP exec: java CentimetersExceptionHandling

Enter the length in feet and inches seperated by a space:
-1 -2

-1 -2
Exception java.lang.IllegalArgumentException -1

----jGRASP: operation complete.


I have to enter the negatives twice to get any results and it is displaying the third input(token)...-1. Also the program does need to continue until valid positive numbers are put in.

[Mattias Ahlin]

Modify your code like this and it'll work:

if (feet > 0 && inches > 0) {
   feetToInches = feet * 12;
   totalInches = inches + feetToInches;
   centimeters = 2.54 * totalInches;
   done = true;
   System.out.println("The total length converted to centimeters is: " + centimeters);
} else {
   System.out.println("Exception: Length cannot be negative.");
}

[ November 28, 2006: Message edited by: Mattias Ahlin ]

[Shananne DuFrame]

Thank you very much!!! This worked..

Could it also work by placing the exception in its own class? This is what I was trying next. Just curious if that could have been another way. Here's what I was trying:

    public class IllegalArgumentException extends CentimetersExceptionHandling
{
public IllegalArgumentException()
{
   super("Cannot use a negative number");
}

public IllegalArgumentException(String strMessage)
{
   super(strMessage)
        }
}

and also change what I had in CentimetersExceptionHandling and create a test program.

[Jesper de Jong]

Your class IllegalArgumentException looks a bit strange.

To start with, IllegalArgumentException is an already existing exception in the package java.lang. It's not a good idea to write your own class with a name that is the same as an already existing, standard Java class.

Also, it's strange that your IllegalArgumentException extends CentimetersExceptionHandling. If you want it to be a real exception class, it should extend class java.lang.Exception.

[Shananne DuFrame]

This is how I finally got it to work, if anyone was curious. Not sure if its quite the correct way to work but my results seem to work so far.

 public class ExceptionHandling extends Exception
{
    public ExceptionHandling()
    {
        super("Cannot be negative");
    }
 
    public ExceptionHandling(String strMessage)
    {
        super(strMessage);
    }
}
   

  import java.util.*;
 
public class ExceptionHandlingProgram
{
    static Scanner console = new Scanner(System.in);
 
    public static void main(String[] args)
    {
 double feet;                             
double inches;  
boolean done;
String str;

done = false;
  
do                          
{
try
{
System.out.print("Enter the feet: ");
feet = console.nextDouble();
            System.out.println();            
 
            System.out.print("Enter the inches: ");         
            inches = console.nextDouble();        
            System.out.println(); 
                     
            if (feet <= 0.0)                    
               throw new IllegalArgumentException();

done = true;
System.out.println("The total length converted to centimeters is: " + (((feet * 12)+ inches)*2.54));
}
catch (IllegalArgumentException iae)
{
System.out.println("Exception "
                              + iae.toString()
+ " Cannot be negative.\n");
}
catch (Exception e)
{
  str = console.next();
            System.out.println("Exception "
                              + e.toString()
+ " " + str +"\n");
}
}
  while(!done);
}
}
  

Thanks again for everyone that responded. It helps learning different techniques and helps me better understand ways of understanding the logics of it.

[Shananne DuFrame]

hehe sorry people, just realized i posted the code I didn't use. Ignore the "public class ExceptionHandling extends Exception". Wasn't used!! Sorry for any confusion.