The ASF copyright must appear on all Java source files. Technically it should appear on all non-binary files in the repository. As you make changes to files, update the copyright to add the current year to the list. The goal is that the copyright notice includes the year in which files change. When creating a new file, don't back date the copyright year ... start with the current year. Try not to change the copyright year on files that haven't actually changed. IntelliJ has a great comparison view: Cmd-9 to see the local changes, the Cmd-D to see the differences. I whip through the changes (using Cmd-forward arrow) and make sure copyrights are up to date as I review the changes prior to a commit.
/** * Apache License * Version 2.0, January 2004 * http://www.apache.org/licenses/ * * Copyright 2008 by chenillekit.org * * Licensed 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 */