Can I use system err println for debugging in java?

It's not a particularly bad habit to have to want to get output when debugging (the worst habit is to not debug).

It's just that we programmers are just so gosh darn lazy. Want output? Look there...

System err println("Got an error: " + e);

That's really easy. You don't need to worry about what logging framework you have, nor what log level it should be at. And this is why we do it all over.

But here's the thing... if you have a project of reasonable size, you have logging in it. If you don't, that's a bad habit. Once you have this logging, and it is something sensible (i.e. not java.util.logging), it's really easy to set up an appender that spits out a standard error.

And to this, there's not really an excuse why not to do it that way.

package c.s.p.m.logging;
import org.apache.log4j.Logger;
public class Main {
    private final static Logger LOG = Logger.getLogger(Main.class);
    public static void main(String[] args) {
        LOG.debug("Oops");
        LOG.info("This is awkward");
        LOG.error("This is bad");
    }
}
and (yep, I'm one of those oddballs that uses the xml format - note that this may not be the optimal one)



    
        
        
            
        
    
    
        
        
        
        
        
        
            
        
    
    
        
        
    
    
        
        
    

and there, in red on my console, I see:
2015-04-30 20:18:34 DEBUG Main:9 - Oops
2015-04-30 20:18:34 INFO  Main:10 - This is awkward
2015-04-30 20:18:34 ERROR Main:11 - This is bad

Meanwhile, in my log file:

2015-04-30 20:18:34 ERROR Main:11 - This is bad

The thing is, there's not really an excuse if you've set it up to just use logging. It's a few more lines in the config file for the console appender.

Once you've got that as a habit to set it up, the logger is much better than System.err ever was and you wonder what took you so long to step away from the println. Time stamps, log levels, line numbers... all for free. You'll find yourself stepping away from that console appender too with a little bit of time. You'll have different log files for different classes (and the aggregate log file too) with a log file watcher. You'll debate putting in crazy appenders...

And best of all, no more silly looks from co-workers because you accidentally checked in a System.err.println() that filled up the console in production.

While System.err.println() isn't bad and isn't a habit that you need to break (as long as you make sure you clean up after yourself and wash your hands afterwards), you will find that once you step away from it there are so many better options out there that are even fewer characters to type.