Simple demo of CSV matching using Regular Expressions
/*
* Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/* Simple demo of CSV matching using Regular Expressions.
* Does NOT use the "CSV" class defined in the Java CookBook, but uses
* a regex pattern simplified from Chapter 7 of <em>Mastering Regular
* Expressions</em> (p. 205, first edn.)
* @version $Id: CSVRE.java,v 1.16 2004/04/25 19:43:32 ian Exp $
*/
public class CSVRE {
/** The rather involved pattern used to match CSV's consists of three
* alternations: the first matches aquoted field, the second unquoted,
* the third a null field.
*/
public static final String CSV_PATTERN = "\"([^\"]+?)\",?|([^,]+),?|,";
private static Pattern csvRE;
public static void main(String[] argv) throws IOException {
System.out.println(CSV_PATTERN);
new CSVRE().process(new BufferedReader(new InputStreamReader(System.in)));
}
/** Construct a regex-based CSV parser. */
public CSVRE() {
csvRE = Pattern.compile(CSV_PATTERN);
}
/** Process one file. Delegates to parse() a line at a time */
public void process(BufferedReader in) throws IOException {
String line;
// For each line...
while ((line = in.readLine()) != null) {
System.out.println("line = `" + line + "'");
List l = parse(line);
System.out.println("Found " + l.size() + " items.");
for (int i = 0; i < l.size(); i++) {
System.out.print(l.get(i) + ",");
}
System.out.println();
}
}
/** Parse one line.
* @return List of Strings, minus their double quotes
*/
public List parse(String line) {
List list = new ArrayList();
Matcher m = csvRE.matcher(line);
// For each field
while (m.find()) {
String match = m.group();
if (match == null)
break;
if (match.endsWith(",")) { // trim trailing ,
match = match.substring(0, match.length() - 1);
}
if (match.startsWith("\"")) { // assume also ends with
match = match.substring(1, match.length() - 1);
}
if (match.length() == 0)
match = null;
list.add(match);
}
return list;
}
}
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