Must be caught or declared? Exceptions

[Shananne DuFrame]

If anyone culd help?? I'm getting this error:
Ch2_Lab.java:53: unreported exception java.io.IOException; must be caught or declared to be thrown
num = Integer.parseInt(keyboard.readLine());
^
Ch2_Lab.java:57: unreported exception java.lang.Exception; must be caught or declared to be thrown
throw new Exception("Exception: Number cannot be negative");
^
2 errors

 import java.io.*;
 
public class Ch2_Lab
{
static BufferedReader keyboard = new
BufferedReader(new InputStreamReader(System.in));

static final double CONVERSION = 2.54;
static final int INCHES_PER_FOOT = 12;

public static void main (String[] args)
{
//declare variables
int feet;
int inches;
int totalInches;
double centimeter;

feet = getNum("feet");
inches = getNum("inches");
System.out.println();

System.out.println("The numbers you entered are "
+ feet + " for feet " + "and "
+ inches + " for inches. ");

totalInches = INCHES_PER_FOOT * feet + inches;
System.out.println();
System.out.println("The total number of inches = "
+ totalInches);

centimeter = totalInches * CONVERSION;
System.out.println("The number of centimeters = "
+ centimeter);

}
public static int getNum(String str)
{
int num = 0;
boolean done = false;
do 
{
try
{
System.out.print("Enter the " + str + ": ");
System.out.flush();
num = Integer.parseInt(keyboard.readLine());
System.out.println();
done = true;
if (num<0)
 throw new Exception("Exception: Number cannot be negative");
}
catch (NumberFormatException nfeRef)
{
System.out.println("Exception" + nfeRef.toString());
}
}
while(!done);
{
return num;
}
}
 
}   

[Paul Sturrock]

You can only throw checked exceptions from a method if the method declares these exceptions, i.e. :

public void doStuff() throws IOException {
 
    throw new IOException("Could not do stuff  :( ");
 
}

If you don't declare the method with "throws" you need to handle the exception within the method. This is because checked exceptions exist to allow the compiler to check that they are properly being handled. Basically the possibility the an operation can fail, and an indication of how it might fail is written into the language to force the coder to handle this possibility.
[ January 25, 2007: Message edited by: Paul Sturrock ]

[Eric Daly]

You are not catching the exceptions being thrown. keyboard.readLine() throws IOException, and you throw just a plain Exception. Then the only catch you consider is a NumberFormatException, though this is never thrown. So all you need is to make sure you catch IOException AND catch Exception (or throw a NumberFormatException instead).

[Paul Sturrock]

Then the only catch you consider is a NumberFormatException, though this is never thrown.

Actually it is thrown (from Integer.parseInt()). But since it is an unchecked exception you don't need to handle it.

[Shananne DuFrame]

Thanks bunches. Got it!!