Pattern.splitAsStream JavaDoc doubt

[Chris Hegarty]

Tagir,

It would seem most useful to update the implementation to
match the current spec. To that end, your first patch looks
like the most appropriate change, pattern-patch.txt.

-Chris.

On 06/12/15 12:21, Tagir F. Valeev wrote:
> Hello!
>
> Currently Pattern.splitAsStream JavaDoc says [1]:
>
>   * <p> If the input sequence is mutable, it must remain constant during the
>   * execution of the terminal stream operation.  Otherwise, the result of the
>   * terminal stream operation is undefined.
>
> However in reality the sequence must remain constant from the stream
> creation till the end of the terminal operation. Let's check:
>
> public static void main(String[] args) {
>      StringBuilder sb = new StringBuilder("a,b,c,d,e");
>      Stream<String> stream = Pattern.compile(",").splitAsStream(sb);
>      // Modify the CharSequence after stream creation
>      sb.setLength(3);
>      // During the terminal operation it remains constant
>      stream.forEach(System.out::println);
> }
>
> The result is:
> a
> Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 3
>      at java.lang.AbstractStringBuilder.charAt(AbstractStringBuilder.java:210)
>      at java.lang.StringBuilder.charAt(StringBuilder.java:76)
> ...
>
> So I feel either the JavaDoc or the implementation should be changed.
> Changing the implementation to fit the JavaDoc is quite simple. See
> the attached pattern-patch.txt and pattern-patch2.txt for two possible
> alternatives.
>
> What do you think?
>
> With best regards,
> Tagir Valeev.
>
> [1] http://hg.openjdk.java.net/jdk9/dev/jdk/file/3c3a5343044c/src/java.base/share/classes/java/util/regex/Pattern.java#l5803
>