try and catch in for statements

Question

how can i rewrite the following code using try and catch statements,catching any exceptions that might be thrown

for (j=0; j<limit; j++)
{
   x=Integer.parseInt(keyboard.readLine());
   y[j]=1/x;
}

Answer 1

That depends if you want the loop to end if there is an error, or you want it to continue...

# loop continues on errors
for ..
  try
    dostuff
  catch something
    fix

vs

# loop ends on errors
try
  for ..
    dostuff
catch something
  ..

Answer 2

Java like pseudocode

for (j=0; j<limit; j++)
{
 try{
   x=Integer.parseInt(keyboard.readLine());
   y[j]=1/x;
 }
 catch(some_exception_not_gonna_say_which_one sengswo){
    //handle exception
 }
}

Answer 3

I am guessing that you want a certain number of integers from the user. A while loop will probably make more sense here than a for loop as you will want to loop until you have the correct number of inputs form the user.

Also, in most cases y[j] is going to hold a zero, as 1 / x is 0 for x > 1. use 1.0/x instead to get floating point math and not integer math.

while j < limit
   try
      // parse number
      // store number
      // increment j
   catch
      // inform user of error
end while

Answer 4

Here is how you can do it in Java. It's better to surround the loop with the try/catch instead of placing the try/catch inside the loop when possible for performance reasons. However, if you want the loop to continue when an error occurs, then you will need to place the try/catch inside the loop.

Loop inside try/catch:

try {
    for (j=0; j<limit; j++)
    {
       x=Integer.parseInt(keyboard.readLine());
       y[j]=1/x;
    }
} catch(Exception e) {
    e.printStackTrace();
}

Loop outside try/catch:

for (j=0; j<limit; j++) {
    try {
        x=Integer.parseInt(keyboard.readLine());
        y[j]=1/x;
    } catch(Exception e) {
        e.printStackTrace();
    }
}

Answer 5

The real question is what do you want to do with the exception (i.e. why even bother catching it)? I would think that you would want to verify or cleanse whatever keyboard input you're getting (IMO a programmer should never trust a user's input), so you would want to ensure that the input is a digit (hint: regex).

There are basically three questions that you need to ask in this scenario: can I recover from this exception, should an exception halt execution, or should I ignore the exception (eat it, and continue to the next number)?