Java has had a native regex package, java.util.regex, since the early-2002 release of Java 1.4.0. It provides powerful and innovative functionality with an uncluttered (if somewhat simplistic) API. It has fairly good Unicode support, clear documentation, and fast execution. It matches against CharSequence objects, so it can be quite flexible in its application.

The original release of java.util.regex was impressive. Its feature set, speed, and relative lack of bugs were all of the highest caliber, especially considering that it was an initial release. The final 1.4 release was Java 1.4.2. As of this writing, Java 1.5.0 (also called Java 5.0) has been released, and Java 1.6.0 (also called Java 6.0 and “Mustang”) is in its second beta release. Officially, this book covers Java 1.5.0, but I’ll note important differences from Java 1.4.2 and the second 1.6 beta where appropriate. (The differences are also summarized at the end of this chapter Image 401.)

Reliance on Earlier Chapters Before looking at what’s in this chapter, it’s important to mention that it doesn’t restate everything from Chapters 1 through 6. I understand that some readers interested only in Java may be inclined to start their reading with this chapter, and I want to encourage them not to miss the benefits of the preface and the earlier chapters: Chapters 1, 2, and 3 introduce basic concepts, features, and techniques ...

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