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 apache-log4j-2.14.1-bin.zip and source package like apache-log4j-2.14.1-src.zip. You can download them at Apache Log4j Website.

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

⏎ org/apache/logging/log4j/core/time/Instant.java

/*
 * 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
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the license for the specific language governing permissions and
 * limitations under the license.
 */
package org.apache.logging.log4j.core.time;

import org.apache.logging.log4j.core.util.Clock;
import org.apache.logging.log4j.util.StringBuilderFormattable;

/**
 * Models a point in time, suitable for event timestamps.
 * <p>
 * Provides methods for obtaining high precision time information similar to the
 * <a href="https://docs.oracle.com/javase/9/docs/api/java/time/Instant.html">Instant</a> class introduced in Java 8,
 * while also supporting the legacy millisecond precision API.
 * </p><p>
 * Depending on the platform, time sources ({@link Clock} implementations) may produce high precision or millisecond
 * precision time values. At the same time, some time value consumers (for example timestamp formatters) may only be
 * able to consume time values of millisecond precision, while some others may require a high precision time value.
 * </p><p>
 * This class bridges these two time APIs.
 * </p>
 * @since 2.11
 */
public interface Instant extends StringBuilderFormattable {
    /**
     * Gets the number of seconds from the Java epoch of 1970-01-01T00:00:00Z.
     * <p>
     * The epoch second count is a simple incrementing count of seconds where second 0 is 1970-01-01T00:00:00Z.
     * The nanosecond part of the day is returned by {@link #getNanoOfSecond()}.
     * </p>
     * @return the seconds from the epoch of 1970-01-01T00:00:00Z
     */
    long getEpochSecond();

    /**
     * Gets the number of nanoseconds, later along the time-line, from the start of the second.
     * <p>
     * The nanosecond-of-second value measures the total number of nanoseconds from the second returned by {@link #getEpochSecond()}.
     * </p>
     * @return the nanoseconds within the second, always positive, never exceeds {@code 999,999,999}
     */
    int getNanoOfSecond();

    /**
     * Gets the number of milliseconds from the Java epoch of 1970-01-01T00:00:00Z.
     * <p>
     * The epoch millisecond count is a simple incrementing count of milliseconds where millisecond 0 is 1970-01-01T00:00:00Z.
     * The nanosecond part of the day is returned by {@link #getNanoOfMillisecond()}.
     * </p>
     * @return the milliseconds from the epoch of 1970-01-01T00:00:00Z
     */
    long getEpochMillisecond();

    /**
     * Gets the number of nanoseconds, later along the time-line, from the start of the millisecond.
     * <p>
     * The nanosecond-of-millisecond value measures the total number of nanoseconds from the millisecond returned by {@link #getEpochMillisecond()}.
     * </p>
     * @return the nanoseconds within the millisecond, always positive, never exceeds {@code 999,999}
     */
    int getNanoOfMillisecond();
}

⏎ org/apache/logging/log4j/core/time/Instant.java

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
Download 

⇒ Source Code for Apache Log4j JDK Logging Adapter

⇐ Source Code for Apache Log4j API

⇑ Downloading and Reviewing Apache Log4j Packages

⇑⇑ FAQ for Apache Log4j