Apache Log4j provides the interface that applications should code to and provides the adapter components required for implementers to create a logging implementation.

Bytecode (Java 1.4) for Apache Log4j is provided in a JAR file like log4j-1.2.17.jar.

Source Code files for Apache Log4j are provided in both binary packge like log4j-1.2.17.zip and source package like log4j-1.2.17-sources.zip. You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j 1.2.17 below.

⏎ org/apache/log4j/helpers/RelativeTimeDateFormat.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.log4j.helpers;

import java.util.Date;
import java.text.FieldPosition;
import java.text.ParsePosition;
import java.text.DateFormat;

/**
   Formats a {@link Date} by printing the number of milliseconds
   elapsed since construction of the format.  This is the fastest
   printing DateFormat in the package.
   
   @author Ceki Gülcü
   
   @since 0.7.5
*/
public class RelativeTimeDateFormat extends DateFormat {
  private static final long serialVersionUID = 7055751607085611984L;


  protected final long startTime;

  public
  RelativeTimeDateFormat() {
    this.startTime = System.currentTimeMillis();
  }
  
  /**
     Appends to <code>sbuf</code> the number of milliseconds elapsed
     since the start of the application. 
     
     @since 0.7.5
  */
  public
  StringBuffer format(Date date, StringBuffer sbuf,
		      FieldPosition fieldPosition) {
    //System.err.println(":"+ date.getTime() + " - " + startTime);
    return sbuf.append((date.getTime() - startTime));
  }

  /**
     This method does not do anything but return <code>null</code>.
   */
  public
  Date parse(java.lang.String s, ParsePosition pos) {
    return null;
  }  
}

⏎ org/apache/log4j/helpers/RelativeTimeDateFormat.java

Or download all of them as a single archive file:

File name: log4j-1.2.17-sources.jar
File size: 481200 bytes
Release date: 2012-05-06
Download 

⇒ Download and Install apache-log4j-1.2.15.zip

⇐ Download and Install log4j-1.2.17.zip

⇑ Downloading Apache Log4j 1.x JAR Packages

⇑⇑ FAQ for Apache Log4j