LogManager addLogger() method in Java with Examples

The addLogger() method of java.util.logging.LogManager is used to insert the specified Logger in this LogManager instance. This Logger must be a named Logger. This method will add this Logger in this LogManager if it does not exist already. If it exists already, then this method returns false.

Syntax:

public boolean addLogger(Logger logger)

Parameters: This method accepts a parameter logger which is the name of the Logger to be inserted in this LogManager instance, if it does not exist already.

Return Value: This method returns a boolean value false, if this Logger does exist already. Else this method does not return anything.

Exceptions: This method throws NullPointerException if the logger to be added is null.

Below programs illustrate addLogger() method:

// Java program to illustrate
// LogManager addLogger() method

import java.util.logging.*;
import java.util.*;

public class GFG {

    public static void main(String[] args)
    {

        // Create LogManager object
        LogManager logManager
            = LogManager.getLogManager();

        Enumeration<String> listOfNames
            = logManager.getLoggerNames();

        System.out.println("Earlier List of Logger Names: ");
        while (listOfNames.hasMoreElements())
            System.out.println(listOfNames.nextElement());

        String LoggerName = "GFG";

        Logger logger
            = Logger.getLogger(LoggerName);

        System.out.println("Adding Logger: " + LoggerName);
        logManager.addLogger(logger);
        listOfNames = logManager.getLoggerNames();

        System.out.println("\nUpdated List of Logger Names: ");
        while (listOfNames.hasMoreElements())
            System.out.println(listOfNames.nextElement());
    }
}

Output:

Earlier List of Logger Names: 
global

Adding Logger: GFG

Updated List of Logger Names: 
GFG
global

Reference: https://docs.oracle.com/javase/9/docs/api/java/util/logging/LogManager.html#addLogger-java.util.logging.Logger-