JDK 8: Second Release Candidate

[Brenden Towey]

I'd like to make a bug report.  Java has had for a while now a bug in 
its regex system which I'd like to see fixed.

The short of it is that the \z pattern does not return 'requiresEnd' and 
it should.

    public void endTest()
    {
       Matcher m = Pattern.compile( "\\z" ).matcher( "" );
       m.find();
       System.out.println( m.requireEnd() );
       assert ( m.requireEnd() );
    }

This prints 'false'.  It shouldn't take much thought to convince 
yourself that if the end of input is required, then 'requiresEnd()' 
should always be true.  There's never a case for the \z pattern that you 
want to match less than all of input.  The above code snippet would make 
a fine unit test for this bug, btw.

You can see the results of this bug if you use other parts of the API, 
for example java.util.Scanner.  Since the the requiresEnd() method 
always returns false, the Scanner will match its own internal buffer 
(usually 1024 characters) and not the end of input.


    public void demo()
    {
       StringBuilder str = new StringBuilder( 4 * 1024 );
       for( int i = 0; i < 1024; i++ ) {
          str.append( i );
          str.append( ',' );
       }
       Scanner s = new Scanner( str.toString() );
       String result = s.useDelimiter( "\\z" ).next();
       String expected = str.toString();
       System.out.println( result.length()+", "+expected.length() );
       assert( expected.equals( result ) );
    }

Output:
C:\Users\Brenden\Dev\proj\Test2\build\classes>java -version
java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b129)
Java HotSpot(TM) 64-Bit Server VM (build 25.0-b69, mixed mode)

C:\Users\Brenden\Dev\proj\Test2\build\classes>java -cp . quicktest.RegexBug
1024, 4010

You can see that the length of the matched string is 1024, not 4010 from 
the original string.

Finally, if you need more convincing, you can test the \Z (capital Z) 
pattern, which does essentially the same thing as \z.  \Z always sets 
its requiresEnd() flag, and it works as expected in the tests above.

Summary: \z should always set its 'requiresEnd' flag.

Thanks for taking the time to read this!



On 2/11/2014 2:31 PM, mark.reinhold at oracle.com wrote:
> Last week a serious flaw in a new API was reported [1].  We decided to
> fix that bug, along with an unrelated JCK failure on Mac OS X [2], so
> we now have a second JDK 8 Release Candidate, build 129.
>
> Binaries available here, as usual: https://jdk8.java.net/download.html
>
>