How to label and license Derivative Works made under Apache License, Version 2.0?

Question

I duplicated a source-code file released under the Apache License, Version 2.0, made very few changes to adapt the code to slightly different situation. So this would seem to be a Derivative Works as defined in part 1 of the license.

The top of that source code has the following text:

/*
 * Copyright 2000-2020 Example Corporation.
 *
 * 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
 *
 * 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.
 */

Exactly how should I change that statement now that I am technically the author but (a) need to acknowledege that I derived this code from existing code of another author, and (b) meet the terms of license?

Do I leave that text block seen above intact as-is? Do I simply add a mention of me above or below that block, stating that I made changes?

Do I change the "Copyright" line to use my name instead? Both my name and the original author's name? The original author does not know of my changes, and did not approve of my changes, so I don't want to imply their involvement or support.

Part 4 item 2 says my modified files must "carry prominent notices stating that You changed the files" but I do not know what exactly that means, nor what is the usual custom.

It would help if someone could post a full example of original versus derived works.

Answer 1

Exactly how should I change that statement now that I am technically the author but (a) need to acknowledege that I derived this code from existing code of another author, and (b) meet the terms of license?

Actually, you are not the author of the file. You are one of the authors, because multiple authors have now made changes to the file.

You must leave that comment block with the copyright and license statements in place, but you should change it to add your own copyright line, making the comment block

/*
 * Copyright 2000-2020 Example Corporation.
 * Copyright 2020 Basil Bourque.
 *
 * 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
 *
 * 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.
 */

This is also customary for satisfying the "prominent notices" of part 4 item 2.

Another custom, that is not required by most licenses but is done anyway, is to add a comment which project you copied the source from, something along the lines of

Copied and adapted from <Original project name> (<link to repository>)

This both acknowledges the original project and makes it clear that they are not responsible for the full contents of the file.