Source Code for Apache Log4j Core Implementation

Apache Log4j Core Implementation provides the functional components of the logging system. Users are free to create their own plugins and include them in the logging configuration. Apache Log4j Core is a required module to use Apache Log4j.

Bytecode (Java 8) for Apache Log4j Core Implementation is provided in a separate JAR file like log4j-core-2.14.1.jar.

Source Code files for Apache Log4j API are provided in both binary packge like and source package like You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j Core Implementation 2.14.1 below.



 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache license, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the license for the specific language governing permissions and
 * limitations under the license.
package org.apache.logging.log4j.core.util;

import java.util.concurrent.locks.LockSupport;

 * This Clock implementation is similar to CachedClock. It is slightly faster at
 * the cost of some accuracy.
public final class CoarseCachedClock implements Clock {
    private static volatile CoarseCachedClock instance;
    private static final Object INSTANCE_LOCK = new Object();
    // ignore IDE complaints; volatile long is fine
    private volatile long millis = System.currentTimeMillis();

    private final Thread updater = new Log4jThread("CoarseCachedClock Updater Thread") {
        public void run() {
            while (true) {
                millis = System.currentTimeMillis();

                // avoid explicit dependency on sun.misc.Util
                LockSupport.parkNanos(1000 * 1000);

    private CoarseCachedClock() {

     * Returns the singleton instance.
     * @return the singleton instance
    public static CoarseCachedClock instance() {
        // LOG4J2-819: use lazy initialization of threads
        CoarseCachedClock result = instance;
        if (result == null) {
            synchronized (INSTANCE_LOCK) {
                result = instance;
                if (result == null) {
                    instance = result = new CoarseCachedClock();
        return result;

     * Returns the value of a private long field that is updated by a background
     * thread once every millisecond. Because timers on most platforms do not
     * have millisecond granularity, the returned value may "jump" every 10 or
     * 16 milliseconds.
     * @return the cached time
    public long currentTimeMillis() {
        return millis;



Or download all of them as a single archive file:

File name: log4j-core-2.14.1-sources.jar
File size: 1281358 bytes
Release date: 2021-03-06


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