RFR: 8293499: Provide jmod --compress option [v4]

[Jaikiran Pai]

On Tue, 13 Sep 2022 09:28:07 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> src/jdk.jlink/share/classes/jdk/tools/jmod/JmodTask.java line 1196:
>> 
>>> 1194:             }
>>> 1195:             try {
>>> 1196:                 int level = Integer.parseInt(value.substring(idx + 1));
>> 
>> If I'm reading this code correctly, then this call to `substring` can potentially end in a `IndexOutOfBoundsException` if the value is `zip-`. Perhaps add a check above to verify that `idx != value.length()`?
>
> `String.substring` does the right thing when `idx == length()` -- it returns the empty string, which would fail to parse. Anyway, I added the test for "zip-" to verify this.

You are right indeed. All these days I had in my mind that the `String.subString` will throw the `IndexOutOfBoundsException` if the passed integer isn't a valid "index". I had that perception due to the javadoc which says:


The substring begins with the character at the specified index

I hadn't paid attention to the later part of that same javadoc which says, along with an example, that the returned value is an empty string if the index == length() and will only throw `IndexOutOfBoundsException` if the passed value is greater than `length()`.

So what you have here is fine, of course. Thank you for updating the test.

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PR: https://git.openjdk.org/jdk/pull/10213