Loggers in Java

Logger (1/3)

The Java API offers an easy to use logging system java.util.logging.

public class LoggerExample {
    private static final Logger logger =
                        Logger.getLogger(LoggerExample.class.getName());
    
    public static void main(String[] args) {
        logger.info("hello logger");
        logger.warning("it is just an example.");
        try {
            throw new IOException("boom");
        } catch (IOException e) {
            logger.log(Level.SEVERE, "oops", e);
        }
    }
}

Logger (2/3)

The logs are printed in the terminal by default. This can be configured and logs can be written in a file.

Jan 25, 2018 7:57:34 PM fr.upem.net.buffers.LoggerExample main
INFOS: hello logger
Jan 25, 2018 7:57:34 PM fr.upem.net.buffers.LoggerExample main
AVERTISSEMENT: it is just an example.
Jan 25, 2018 7:57:34 PM fr.upem.net.buffers.LoggerExample main
GRAVE: oops
java.io.IOException: boom
    at fr.upem.net.buffers.LoggerExample.main(LoggerExample.java:15)

You can set ommit the INFO logs.

logger.setLevel(Level.WARNING);

Logger (3/3)

The logger offers different level of logs

• SEVERE
• WARNING
• INFO
• FINE,FINER,FINEST

Warning the level FINE,FINER and FINEST are not available by default.
You can use INFO to debug type logs.