Name: nt126004 Date: 09/04/2001


java version "1.4.0-beta2"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta2-b77)
Java HotSpot(TM) Client VM (build 1.4.0-beta2-b77, mixed mode)


The regex parser is too simplistic in determining whether a
caret in a character class should be treated as a negation
operator. The first run of the sample program below shows a
properly-working character class: the caret matches a literal
caret because it's not the first character in the class. The
second regex, with the caret right after the escaped left-
bracket, should work the same, but it doesn't match the carets
in the target string any more. In the third run, we can see
that the caret is actually negating the rest of the class, in
this case cancelling out the first at-sign.



//====================== sample code ===========================

import java.util.regex.*;

public class PatternTest
{
  public static void main(String[] argv)
  {
    Pattern p1 = Pattern.compile(argv[0]);
    Matcher m1 = p1.matcher("@@@@[[[[^^^^");
    System.out.println(m1.find() ? "found: " + m1.group()
                                 : "not found");
  }
}

//======================== output =============================

$ java PatternTest '[\[@^]+'
found: @@@@[[[[^^^^


$ java PatternTest '[@\[^]+'
found: @@@@[[[[


$ java PatternTest '[@\[^@]+'
found: [[[[
(Review ID: 131194)
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