RFR: 8305457: Implement java.io.IO [v3]

[Stuart Marks]

On Wed, 8 May 2024 13:13:33 GMT, Pavel Rappo <prappo at openjdk.org> wrote:

>> I haven't given it a try, but a brief look at the code suggests that if the console implementation backed by JLine gets used, then a `null` prompt may not generate a `NullPointerException` (since JLine appears to allow `null`) whereas if the internal JDK console implementation gets used then a `NullPointerException` will get thrown. If the expectation is to disallow a `null` prompt, then perhaps `Objects.requireNonNull(prompt)` before we hand off to the underlying console implementations might be required.
>
> Good catch! `jdk.internal.org.jline.JdkConsoleProviderImpl.JdkConsoleImpl.readln(null)` does not throw `NullPointerException` (NPE), which it must. I'll fix the bug and add a test.
> 
> Speaking of NPE. The newly added `Console.print` and `Console.println` methods do not throw NPE if passed null. While that's how it should be, they don't specify that, so the class-level NPE clause applies:
> 
>     * Unless otherwise specified, passing a {@code null} argument to any method
>     * in this class will cause a {@link NullPointerException} to be thrown.
>     ...
>     public sealed class Console implements Flushable permits ProxyingConsole {
> 
> I'll fix that.
> 
> We should also specify NPE (or absence thereof) on methods of `IO`. Otherwise, this package clause applies:
> 
>     * Unless otherwise noted, passing a {@code null} argument to a constructor or
>     * method in any class or interface in this package will cause a
>     * {@code NullPointerException} to be thrown.
>     ...
>     package java.io;
> 
> @stuart-marks speaking of exceptions. Do we need to add explicit `@throws` tag to `IO` methods?
> 
>     @throws {@code IOError} if {@code System.console()} returns {@code null}
> 
> While it would make sense, it would also look superfluous: we already specify that error condition in the class comment and then in every method's main description. Do we need to add one more note on `IOError`?

Most of these are defined in terms of `String.valueOf(Object)` which if passed a null reference will return the String object containing `null`. So no, I don't think NPE should be thrown. It might be worth mentioning this explicitly somewhere though.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19112#discussion_r1594282580