How to Format Java Logging Output to Appear on a Single Line

How can I format my Java logging output to display on a single line using java.util.logging?

import java.util.logging.Logger;
import java.util.logging.ConsoleHandler;
import java.util.logging.SimpleFormatter;

public class CustomLogger {
    private static final Logger logger = Logger.getLogger(CustomLogger.class.getName());

    public static void main(String[] args) {
        ConsoleHandler handler = new ConsoleHandler();
        handler.setFormatter(new SingleLineFormatter());
        logger.addHandler(handler);

        logger.info("MyLogMessageHere");
    }
}

To format your Java logging output to appear on a single line when using java.util.logging, you will need to create a custom formatter. This formatter will override the default multi-line output and ensure that log messages are displayed in your desired format.

import java.util.logging.Formatter;
import java.util.logging.LogRecord;

class SingleLineFormatter extends Formatter {
    @Override
    public String format(LogRecord record) {
        return String.format("%1$tF %1$tT %2$s - %3$s%n", 
                             record.getMillis(), 
                             record.getSourceClassName(), 
                             record.getMessage());
    }
}

Causes

• The default formatting of java.util.logging uses multiple lines for clarity, separating timestamps, class info, and log messages.
• By default, the formatter will include line breaks which can be unpreferred in certain logging scenarios.

Solutions

• Create a custom log formatter by extending the `Formatter` class.
• Override the `format` method to concatenate log information into a single line.

Mistake: Not overriding the `formatMessage` method in addition to `format`.

Solution: Always use `format` to customize the output. The `formatMessage` method is useful but not essential for changing the line format.

Mistake: Forgetting to attach the custom formatter to your logger handler.

Solution: Ensure that you set the formatter on the logger handler before logging any messages.