Creating Log Messages

package io.entityfour.logmodule;

import java.util.logging.Logger;

public class LogExample {

    private static final Logger LOGGER = Logger.getLogger(LogExample.class.getName()); // Instantiating the logger here, whilst setting its accessibility to private and final, is a better approach. Note that the instance name is now LOGGER as it is a constant / final.

    public static void main(String[] args) {
        // Logger.getLogger(); // This will set up a basic logger, however, it is common to give the logger a name!

        // Logger.getLogger(LogExample.class.getName()); // Convention is that the logger name is the same as the class name. You can use the <classname>.class.getName() method to do this for you.

        //Logger logger = Logger.getLogger(LogExample.class.getName()); // Instantiate the logger. This can be done here in the method, however, it is better for this to be encapsulated and include above the class. This way, a private modifier can be used so that the logger is exclusive to this class.

        // logger.log(Level.INFO, "This is an example INFO level log)"); // The log() method takes a log level, followed by a message as it arguments. It will log to the console by default!

        LOGGER.log(Level.INFO, "This is a new INFO level log message"); // As the logger has now been created as a constant / final, it can be called by its new instance name.
    }
}

package io.entityfour.logmodule;

import java.util.logging.Logger;

public class LogExample {

    private static final Logger LOGGER = Logger.getLogger(LogExample.class.getName());

    public static void main(String[] args) {

        LOGGER.setLevel(Level.FINEST); // Set the Logger's level to FINEST
        LOGGER.log(Level.FINEST, "This is a mighty fine message"); // This will not print! Despite the Logger's level being set above, the Handler's level has not been set!
    }
}

package io.entityfour.logmodule;

import java.util.logging.Logger;

public class LogExample {

    private static final Logger LOGGER = Logger.getLogger(LogExample.class.getName());

    static { // This is known as an 'Initializer Block'. Cod e that is declared here will run each time an instance of the object (Class) is created.
        LOGGER.setLevel(Level.FINEST);
        ConsoleHandler consoleHandler = new ConsoleHandler(); // Instantiate a ConsoleHandler
        consoleHandler.setLevel(Level.FINEST); // Set the Handlers level to FINEST
        LOGGER.addHandler(consoleHandler); // Assign the handler to the logger
    }

    public static void main(String[] args) {
        LOGGER.log(Level.FINEST, "This is a mighty fine message"); 
    }
}

package io.entityfour.logmodule;

import java.util.logging.Logger;

public class LogExample {

    private static final Logger LOGGER = Logger.getLogger(LogExample.class.getName());

    static {
        FileHandler fileHandler = null; // Create a FileHandler object with a null value
        try { // Wrap the fileHandler instantiation with try/catch to catch any exceptions
            fileHandler = = new FileHandler(<className>.class.getSimpleName() + ".log");
        } catch (IOException e){
            e.printStackTrace();
        }
        LOGGER.addHandler(fileHandler); // Assign the handler to the logger
    }

    public static void main(String[] args) {
        LOGGER.log(Level.FINEST, "This is a mighty fine message"); 
    }
}

LOGGER.log(Level.<LOGLEVEL>, <STR_MESSAGE>);

LOGGER.logp(Level.<LOGLEVEL>, <CLASSNAME>.class.getName(), <STR_METHODNAME>, <STR_MESSAGE>);

LOGGER.logrb(Level.<INFO>, ResourceBundle.getBundle("en_US"), <STR_MESSAGE>);