Catching an exception when terminating a program in JAVA

Question

Is there a way to do this?

I'm coding a program that has to iterate for a very long time, and while doing so it is supposed to write to file. I want to close the stream as soon as I terminate the program manually and by doing so, avoid the risk of loosing data because of the unclosed stream. There should be a way of doing this with exception handling, but I'm not sure. Any kind of suggestion is very appreciated!

Thank you

Use a try-finally clause where the streams are closed in the finally block. Or, if you're using Java 7, use the try-with-resources block. — FThompson
– FThompson, Commented Dec 9, 2012 at 23:30

AlexWien · Accepted Answer · 2012-12-09 23:34:18Z

2

in main:

try {
   startapp();
} finally {
   closeAll();
}

in closeAll() you do what you do for a safe shutdown The code in the finally block will executed even when exceptions will ocure.

answered Dec 9, 2012 at 23:34

AlexWien

28.9k6 gold badges56 silver badges84 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

ccoutinho Over a year ago

It didn't work... But I found a way out, I will post it in a few seconds

AlexWien Over a year ago

this works! only if you call System.exit() what you never shoul do, it will not work. or when the vm crashes with internal error

Perception · Accepted Answer · 2012-12-09 23:44:30Z

1

Using exceptions to control program execution the way you are describing is poor design. It's would be much better to use a shutdown hook.

Runtime.getRuntime().addShutdownHook(new Thread() {
    @Override
    public void run() {
       // Close streams here
    }
});

This will handle most normal shutdowns just fine, though in the case of a hard halt (SIGKILL) the shutdown hooks are not guaranteed to be run. But that is no worse than if you were attempting to close the stream via a finally block.

edited Dec 9, 2012 at 23:44

answered Dec 9, 2012 at 23:36

Perception

80.8k19 gold badges190 silver badges197 bronze badges

2 Comments

ccoutinho Over a year ago

I tried to test this, but I wasn't able to compile... Still, I already found the problem.

Perception Over a year ago

The code above does compile and work for me. What problems did you run into?

ccoutinho · Accepted Answer · 2012-12-09 23:45:27Z

0

I found a way! I lost so much time with this, without noticing that streams are automatically closed when the program terminates...

Data hadn't been written because I wasn't using the flush() method after the write() method, like this:

out.write(line);
out.flush();

Thank you all for your help

answered Dec 9, 2012 at 23:45

ccoutinho

4,7926 gold badges53 silver badges59 bronze badges

1 Comment

AlexWien Over a year ago

this is not an answer to your question! close the file, when you dont need it anymore. out.close()

Collectives™ on Stack Overflow

Catching an exception when terminating a program in JAVA

3 Answers 3

2 Comments

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related