Upgrade to Java 9

[Zhiyuan-Amos]

Java 9 will be released on 21st September is released!

Some changes that we can look into:

1. Convert method calls like Arrays#asList(...) to use List#of(...). https://dzone.com/articles/java-9-factory-methods-to-create-immutable-collect
2. Look into using Runtime.Version. https://dzone.com/articles/process-api-and-version-in-java-9

[Zhiyuan-Amos]

@damithc Can we upgrade the code base to use Java 9? This fixes #374 too.

[damithc]

I guess we can, as long as we do that quickly, before students start on level 4.

[Zhiyuan-Amos]

@yamidark take a look at what I've done so far for Java 9 on my branch. I'm not too sure whether we need to upgrade Gradle or not though, this seems like there's a need to upgrade to 4.2.1, but I'm not too sure, maybe you can try.

[damithc]

It's too late for this sem but we have to make the project Java 9 compatible by next sem. I thought there is no hurry because Java is normally backward compatible but apparently AB4 runs into issues in Java 9 environments.

[Zhiyuan-Amos]

Ah I see; I thought students were still using Java 8. I'll look into it.

[damithc]

I thought students were still using Java 8.

CS2030 uses Java 9; that's why some students are already on Java 9 when they come to CS2103. In any case, we should ensure compatibility with the latest public version as soon as it is out (but we can wait a while before we make the latest version a prerequisite)

[pyokagan]

@Zhiyuan-Amos

Convert method calls like Arrays#asList(...) to use List#of(...). https://dzone.com/articles/java-9-factory-methods-to-create-immutable-collect
Look into using Runtime.Version. https://dzone.com/articles/process-api-and-version-in-java-9

Can split this into separate issues? I guess they will be lower priority as well (and maybe first-timers?)

I think this issue, as it is, has been resolved and can be closed.

[Zhiyuan-Amos]

@pyokagan noted.

Closing this issue, for other updates that we can make to our codebase, see #871 and #872.