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Thread: Exception Handling

  1. #1

    Default Exception Handling

    Hi all, I am new to this forum so please be patient with me. I am a new programmer and I seem to be confused with the concept of exception handling. If we are to write code that would try a statement then catch the error, why wouldn't we be able to just anticipate that an error would occur and re-write the code so there wouldn't be a runtime/compile error, therefore eliminating the need of the try/catch statements? Am I missing something here? Thanks!


  2. #2
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    Default Re: Exception Handling

    Well your are confusing compile time errors with run time errors. For example, if you were to accidentally forget to add a bracket for your construct:

    public class test {
    public test() {
    }
    That is a compile time error, something the compiler can realistically predict. Where-as run time errors are things that having a compiler predict would either be far too expensive (performance wise), or just down right impossible (at this time).

    public class test {

    public static void main(String[] args) {

    try(BufferedReader br = new BufferedReader(new FileReader("file\\test.txt"))) {


    }
    catch(IOException ioe) { System.out.println("you see Linux power you had that file on your computer like you were supposed to, however your clients were either blocking access or didn't have that file");}


    }
    }

  3. #3
    Super Moderator jps's Avatar
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    Default Re: Exception Handling

    Quote Originally Posted by LinuxPower View Post
    why wouldn't we be able to just anticipate that an error would occur and re-write the code so there wouldn't be a runtime/compile error, therefore eliminating the need of the try/catch statements? Am I missing something here? Thanks!
    What code do you write to predict a hardware device fails, or the network being interrupted, or power going out, or even things like users giving bad input? The try/catch IS the way we handle these situations. You expect this thing the code is doing to work, but sometimes it just does not work out, and the code needs to respond.
    For example, you go to the ATM and withdraw money, and there was no try/catch. Suppose the cash dispenser tears up a bill and fails to give out cash. The program told it to give your cash and deducts the amount from your balance leaving you with no cash. On the other hand with the try/catch, when the dispenser fails and throws the exception the program can prevent itself from adjusting your balance knowing no cash was given.

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    LinuxPower (September 6th, 2013)

  5. #4

    Default Re: Exception Handling

    Sounds a bit more clear now. Thanks!

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    Default Re: Exception Handling

    There are some situations where you can code to avoid an exception rather than use a try/catch statement.
    if(denom != 0) {
        result = num / denom;
    }
    But if you wish to call a method that throws an exception you have no choice but to use try/catch. "So why does that method throw an exception?" I hear you ask. Because the author has no way to determine the almost infinite ways that something can go wrong nor anticipate how you want the code to perform if it does go wrong. Therefore the method throws the exception and whoever called it can handle it however they want.
    Improving the world one idiot at a time!

  7. The Following 2 Users Say Thank You to Junky For This Useful Post:

    jps (September 3rd, 2013), LinuxPower (September 6th, 2013)

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