CODEWITHSUNDEEP
java
Oh Fiveight
Oh Fiveight

Reputation: 475

Running a section of code again in Java

I am a Java beginner having some trouble. I have a try-catch block where the try portion tries to run a section of code and the catch portion runs different code if the try code throws any sort of error. It looks something like:

try {
    <code to try>
} catch(Exception e) {
    <various variable reassignments>
    <run "try" code again>  (what I don't know how to do)
}

I think this involves some sort of loop, which I am fairly familiar with using, but I don't know how I would format it to work in this scenario.

Upvotes: 1

Views: 1868

Answers (7)

doublesharp
doublesharp

Reputation: 27599

You can either place your entire try/catch block into a loop, or make a method call from the try and catch. Note that if you use a loop you'll need some logic in place to prevent an infinite loop if you throw an Exception every time, even after updating your variable values.

Make a method call

String arg = "foo";
try {
   Object.method(arg); // your code, taking your variable as an argument
} catch (Exception e){
   arg = "bar";        // update variable value
   Object.method(arg); // call your code again
}

Use a loop

while (true){
    try {
        // ... your code, which might throw an Exception
        break;  // break if there are no exceptions
    } catch (Exception e){
        // assign vars
    }
}

Upvotes: 2

vezenkov
vezenkov

Reputation: 4145

Refactor the <code to try> into a separate method. Call it inside both try and catch. This way you will achieve something like a single retry. Another option is to put the whole try catch into a while loop and control how many retries you want using a variable and depending on the result you could initialize different variables.

Upvotes: 1

JonCav
JonCav

Reputation: 1667

You can encase the entire try/catch into a for/while loop that will exit when the try successfully runs. 

while (true) {
    try {
         <code to try>
         //exit on success
           } catch(Exception e) {
                 <various variable reassignments>                 
                   }
 }

Upvotes: 0

Avihoo Mamka
Avihoo Mamka

Reputation: 4786

You can wrap it with while loop, And then if you didn't get to the success = true assignment and got to the catch section, do your coding and the while loop will run again the try-catch section.

For example:

boolean success = false;
while (!success) {
  try {
      <code to try>
      success = true;
      } catch(Exception e) {
        <various variable reassignments>
      }
}

Upvotes: 0

Mena
Mena

Reputation: 48404

This underlines a small architectural problem.

There's no implicit looping in try/catch blocks: you try and recover if an Exception is thrown.

What you can do is, from best to worst:

  1. Place the try code in a method, parametrizable as needed so its behavior can change when invoked again. Then invoke that method with different arguments in the try and catch blocks.

    Note that in this case, the invocation in your catch block might throw that same Exception again, which you might assume is not recoverable at that point.

  2. Use nested try / catch blocks, where you vary the procedure from your try block within a try block nested in your catch block.

    This is ok but less readable.

    Multiple nested try / catch blocks will severely reduce your readability though.

  3. Place the whole try / catch in a loop whose break condition is defined in all terminations (otherwise you might be looping forever and logging tons of stack traces)

    This would be acceptable in theory but is usually the recipy for disaster over time.

Upvotes: 2

ryachza
ryachza

Reputation: 4540

I think you want something like:

boolean run = true;
while(run)
{
    try
    {
        // do action
        run = false;
    }
    catch(Exception e)
    {
        // do whatever actions
        // when you want to break, set run = false
    }
}

Upvotes: 0

Jan D
Jan D

Reputation: 883

You could break the loop if successful, and stay in it in case of an exception:

while (true) {
    try {
         <code to try>
         break; // operations were successful, so leave the loop!
    } catch(Exception e) {
         <various variable reassignments>
         // do not break, i.e. run "try" code again
    }
}

Upvotes: 4

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