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Java Cookbook
book

Java Cookbook

by Ian F. Darwin
June 2001
Intermediate to advanced content levelIntermediate to advanced
888 pages
21h 1m
English
O'Reilly Media, Inc.
Content preview from Java Cookbook

Printing All Occurrences of a Pattern

Problem

You need to find all the strings that match a given RE in one or more files or other sources.

Solution

This example reads through a file using a ReaderCharacterIterator , one of four CharacterIterator classes in the Jakarta RegExp package. Whenever a match is found, I extract it from the CharacterIterator and print it.

The other character iterators are StreamCharacterIterator (as we’ll see in Chapter 9, streams are 8-bit bytes, while readers handle conversion among various representations of Unicode characters), CharacterArrayIterator, and StringCharacterIterator. All of these character iterators are interchangeable; apart from the construction process, this program would work on any of them. Use a StringCharacterIterator, for example, to find all occurrences of a pattern in the (possibly long) string you get from a JTextArea’s getText( ) method, described in Chapter 13.

This code takes the getParen( ) methods from Section 4.6, the substring method from the CharacterIterator interface, and the match( ) method from the RE, and simply puts them all together. I coded it to extract all the “names” from a given file; in running the program through itself, it prints the words “import”, “org”, “apache”, “regexp”, and so on.

> jikes +E -d . ReaderIter.java
> java ReaderIter ReaderIter.java
import
org
apache
regexp
import
java
io
import
com
darwinsys
util
Debug
Demonstrate
the
Character
Iterator
interface
print

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Publisher Resources

ISBN: 0596001703Supplemental ContentCatalog PageErrata