Friday, January 28, 2011

regexp's in Java...
Regular Expressions In JAVA
The JAVA class library provides two classes to support regexes in JAVA, namely Pattern and Matcher from the java.util.regex package. Pattern simply stores a regex that we want to match strings against. We can get a Matcher object by matching a Pattern against a String, and then use the Matcher object to see if the pattern matched, extract captures, etc.
An Annoying JAVA Issue
Many regexes use sequences such as \d to match a digit. As in many programming languags, a regex in JAVA is represented as a string. This is a problem because "\d" is seen by the JAVA compiler as a JAVA escape sequence, and the compiler will complain that it doesn't understand the escape sequence \d. Therefore, it is important to add extra backslashes, e.g. "\\d". Be careful - in the case of \b this will go quietly un-noticed at compile time, then your regex won't work out as you expect at runtime.

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