During the discussions in https://github.com/openjdk/jdk/pull/29433, I looked at the source code of `MediaTracker` and found several issues for cleaning up.
- The `target` field in `MediaTracker` is initialised in the constructor, it's never changed; - The visibility of the `head` field in `MediaTracker` can be reduced to `private`; - The `tracker` and `ID` fields in the `MediaEntry` class are never changed after being set in the constructor, therefore it's `final`; - The `getID` method of `MediaEntry` should be `final`, subclasses shouldn't be able to change the returned id; - The fields in `ImageMediaEntry`—`image`, `width` and `height`—can also be `final`. - The `ImageMediaEntry` class itself is `final`. Additionally, I added the `@Override` annotation to overridden methods. ------------- Commit messages: - 8378585: Mark fields in MediaTracker final Changes: https://git.openjdk.org/jdk/pull/29899/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29899&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8378585 Stats: 14 lines in 1 file changed: 4 ins; 0 del; 10 mod Patch: https://git.openjdk.org/jdk/pull/29899.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/29899/head:pull/29899 PR: https://git.openjdk.org/jdk/pull/29899
