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package com.darwinsys.csv;

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.
 * Attempts to follow RFC 4180 (https://www.ietf.org/rfc/rfc4180.txt),
 * but with no provision ATM for the header line.
 * Does NOT use the "CSV" class defined in the Java CookBook, but uses
 * a regex pattern simplified from Chapter 7 of Mastering Regular
 * Expressions (p. 205, first edn.)
 * Example usage:
 * 
 * public static void main(String[] argv) throws IOException {
 * 	System.out.println(CSV_PATTERN);
 * 	new CSVRE().process(new BufferedReader(new InputStreamReader(System.in)));
 * }
 * 
*/ // tag::main[] // package com.darwinsys.csv; public class CSVRE implements CSVParser { /** * The pattern used to match CSVs consists of three alternations; * the first matches a quoted field, the second unquoted, * the third a null field. */ public static final String CSV_PATTERN = "\"([^\"]+?)\",?|([^,]+),?|,"; private final static Pattern csvRE = Pattern.compile(CSV_PATTERN); private static boolean debug = true; // Not final for debugger use. public static void main(final String[] argv) throws IOException { System.out.println(CSV_PATTERN); new CSVRE().process( new BufferedReader(new InputStreamReader(System.in))); } /** Process one file. Delegates to parse() a line at a time * @param input the Reader containing the data to parse * @throws java.io.IOException If the reader does */ public void process(final BufferedReader input) throws IOException { String line; // For each line... while ((line = input.readLine()) != null) { System.out.println("Input line = `" + line + "'"); final List list = parse(line); System.out.println("Found " + list.size() + " items."); for (String str : list) { System.out.print(str + ","); } System.out.println(); } } /** Parse one line. Not static to allow constructor args later. * @param line the input * @return List of Strings, minus their double quotes */ public List parse(final String line) { final List list = new ArrayList<>(); final 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("\"")) { // must also end with \" if (!match.endsWith("\"")) { throw new IllegalArgumentException( "Quoted column missing end quote: " + line); } match = match.substring(1, match.length() - 1); } list.add(match); } return list; } } // end::main[]




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