RFR: 8364361: [process] java.lang.Process should implement Closeable [v24]

[Pavel Rappo]

On Mon, 27 Oct 2025 18:42:32 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> The teardown of a Process launched by `ProcessBuilder` includes the closing of streams and ensuring the termination of the process is the responsibility of the caller. The `Process.close()` method provides a clear and obvious way to ensure all the streams are closed and the process terminated.
>> 
>> The try-with-resources statement is frequently used to open streams and ensure they are closed on exiting the block. By implementing `AutoClosable.close()` the completeness of closing the streams and process termination can be done by try-with-resources.
>> 
>> The actions of the `close()` method are to close each stream and destroy the process if it has not terminated.
>
> Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add \@implNote to recommend overriding close and calling `super.close()`.

Roger, I'm thinking about that example in `close()`. It would be a ready-to-run program, if not for the method name: `example`. Since the text already says that it's an example, we could rename the method to `main` without loss of information.

This way the example could be pasted into a file and run, thanks to JEP 512: Compact Source Files and Instance Main Methods. Note, I used `var` for the reader and writer to get rid of imports from `java.io`, but it's not essential as a decent IDE would insert them on paste.


void main() {
    try (Process p = new ProcessBuilder("cat").start();
         var writer = p.outputWriter();
         var reader = p.inputReader()) {
        writer.write(haiku);
        writer.close();
        // Read all lines and print each
        reader.readAllLines()
                .forEach(System.out::println);
        var status = p.waitFor();
        if (status != 0) {
            throw new RuntimeException("unexpected process status: " + status);
        }
    } catch (Exception e) {
        System.out.println("Process failed: " + e);
    }
}

String haiku = """
        Oh, the sunrise glow;
        Paddling with the river flow;
        Chilling still, go slow.
        """;

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PR Comment: https://git.openjdk.org/jdk/pull/26649#issuecomment-3469753255