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mkyongmkyong
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csv
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‎java-io/pom.xml‎

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<version>1.20</version>
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</dependency>
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<!-- csv file -->
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<dependency>
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<groupId>com.opencsv</groupId>
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<artifactId>opencsv</artifactId>
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<version>5.3</version>
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</dependency>
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</dependencies>
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<build>

‎java-io/src/main/java/com/mkyong/io/csv/CsvFileReader.java‎

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package com.mkyong.io.csv;
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import java.io.File;
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import java.util.List;
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public interface CsvFileReader {
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List<String[]> read(File file) throws Exception;
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}

‎java-io/src/main/java/com/mkyong/io/csv/CsvFileReaderOpenCsv.java‎

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package com.mkyong.io.csv;
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import com.opencsv.CSVReader;
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import java.io.File;
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import java.io.FileReader;
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import java.util.List;
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public class CsvFileReaderOpenCsv implements CsvFileReader {
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@Override
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public List<String[]> read(File file) throws Exception {
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List<String[]> result;
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try (CSVReader reader = new CSVReader(new FileReader(file))) {
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result = reader.readAll();
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}
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return result;
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}
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}

‎java-io/src/main/java/com/mkyong/io/csv/CsvParserSimple.java‎

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package com.mkyong.io.csv;
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import java.io.IOException;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* https://tools.ietf.org/html/rfc4180
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* <p>
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* Fields containing line breaks (CRLF), double quotes, and commas
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* should be enclosed in double-quotes. For example:
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* <p>
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* "aaa","b CRLF
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* bb","ccc" CRLF
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* zzz,yyy,xxx
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* <p>
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* If double-quotes are used to enclose fields, then a double-quote
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* appearing inside a field must be escaped by preceding it with
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* another double quote. For example:
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* <p>
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* "aaa","b""bb","ccc"
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*/
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public class CsvParserSimple {
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private static final char DEFAULT_SEPARATOR = ',';
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private static final char DEFAULT_QUOTE_CHARACTER = '"';
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public String[] parseLine(String line) throws IOException {
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return parseLine(line, DEFAULT_SEPARATOR);
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}
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public String[] parseLine(String line, char separator) throws IOException {
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return parseLine(line, separator, DEFAULT_QUOTE_CHARACTER);
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}
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public String[] parseLine(String line, char separator, char quoteChar) throws IOException {
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return parse(line, separator, quoteChar).toArray(String[]::new);
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}
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private List<String> parse(String line, char separator, char quoteChar) {
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List<String> result = new ArrayList<>();
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boolean inQuotes = false;
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boolean startCollectChar = false;
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boolean doubleQuotesInColumn = false;
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StringBuilder field = new StringBuilder();
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// convert line to char[] and loop one by one
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for (char c : line.toCharArray()) {
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if (c == quoteChar) {
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inQuotes = !inQuotes;
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} else {
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// if find separator and not in quotes, add chars to a field.
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if (c == separator && !inQuotes) {
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result.add(field.toString());
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field.setLength(0);
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} else {
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// else add the char into a field
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field.append(c);
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}
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}
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}
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//line done, what to do? if remaining, add to result
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if (field.length() > 0) {
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result.add(field.toString());
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}
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return result;
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}
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/*public static List<List<String>> read(File file) throws Exception {
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List<List<String>> result = new ArrayList<>();
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try (BufferedReader br = new BufferedReader(new FileReader(file))) {
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String line;
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while ((line = br.readLine()) != null) {
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List<String> strings = parseLine(line, ',', '"');
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result.add(strings);
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}
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}
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return result;
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}*/
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}

‎java-io/src/main/java/com/mkyong/io/csv/SingleClassCsvReader.java‎

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package com.mkyong.io.csv;
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import java.io.BufferedReader;
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import java.io.Reader;
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import java.util.LinkedList;
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import java.util.List;
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public class SingleClassCsvReader {
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public static final char LF = '\n';
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public static final char CR = '\r';
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public static final char COMMA = ',';
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public static final char DOUBLE_QUOTE = '"';
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/**
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* Core implementation for reading csv-values from a {@link java.io.Reader}
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* @param reader Source for reading.
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* @param delimiter Delimiter character. Default is a comma(,).
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* @param quote Quote character. Default is a double quote char(").
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* @return List of read Csv lines.
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* @throws Exception If an error happens whilst reading.
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*/
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public static List<List<String>> read(Reader reader, char delimiter, char quote) throws Exception{
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if(reader == null){
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throw new Exception("missing reader",
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new IllegalArgumentException(new NullPointerException("reader")));
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}
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if(delimiter == ' '){
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delimiter = COMMA;
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}
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if(quote == ' '){
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quote = DOUBLE_QUOTE;
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}
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BufferedReader buff = null;
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try {
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//Create an underlying reader to keep original reader's reference
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buff = new BufferedReader(reader);
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List<List<String>> csv = new LinkedList<List<String>>();
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String line = null;
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while((line = buff.readLine()) != null){
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csv.add(readLine(line, delimiter, quote));
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}
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return csv;
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}catch(Exception e){
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throw e;
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}finally{
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if(buff != null){
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try{
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buff.close();
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buff = null;
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}catch(Exception e){
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throw e;
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}
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}
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}
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}
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/**
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* Core implementation for reading csv-values within text line.
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* @param line Csv text line
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* @param delimiter Delimiter character. Default is a comma(,).
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* @param quote Quote character. Default is a double quote char(").
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* @return List of read Csv values.
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*/
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public static List<String> readLine(String line, char delimiter, char quote) {
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if(line == null)
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line = "";
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if(delimiter == ' ')
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delimiter = COMMA;
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if(quote == ' ')
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quote = DOUBLE_QUOTE;
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List<String> values = new LinkedList<String>();
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char[] chars = line.toCharArray();
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StringBuffer value = new StringBuffer("");
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boolean quoted = false;
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for (int i = 0; i < chars.length; i++) {
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char c = chars[i];
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if(CR == c)
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continue;
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if(LF == c) {
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values.add(value.toString());
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value = new StringBuffer();
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break;
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}
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if(quoted) {
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if(quote == c) {
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if((i+1) < chars.length && chars[i+1] == quote) {
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value.append(quote);
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i++;
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}else {
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quoted = false;
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}
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}else if(delimiter == c) {
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value.append(c);
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}else {
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value.append(c);
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}
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}else {
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if(quote == c) {
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quoted = true;
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if(
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((i+1) < chars.length && chars[i+1] == delimiter) &&
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((i-1) >= 0 && chars[i-1] != delimiter)
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) {
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quoted = false;
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value.append(c);
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}
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} else if(delimiter == c) {
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values.add(value.toString());
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value = new StringBuffer();
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} else{
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value.append(c);
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}
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}
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}
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if(value.length()>0) {
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values.add(value.toString());
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}
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return values;
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}
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}

‎java-io/src/main/java/com/mkyong/io/csv/test/CSVReaderSimple.java‎

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package com.mkyong.io.csv.test;
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import java.io.BufferedReader;
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import java.io.FileReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.util.List;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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public class CSVReaderSimple {
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private static final String CSV_SEPARATOR = ",";
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public static void main(String[] args) {
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//readCSVFile("csv/country.csv", CSV_SEPARATOR);
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readCSVFileJava8("csv/address.csv", CSV_SEPARATOR);
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}
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private static void readCSVFileJava8(String fileName, String csvSeparator) {
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String line;
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try (BufferedReader br = new BufferedReader(
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new InputStreamReader(
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CSVReaderSimple.class.getClassLoader().getResourceAsStream(fileName)))) {
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while ((line = br.readLine()) != null) {
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// split by a comma separator
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List<String> split = Stream.of(line.split(csvSeparator)).collect(Collectors.toList());
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System.out.println("\nLength : " + split.size());
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split.forEach(System.out::println);
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}
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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private static void readCSVFile(String fileName, String csvSeparator) {
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String line;
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try (BufferedReader br = new BufferedReader(
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new InputStreamReader(
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CSVReaderSimple.class.getClassLoader().getResourceAsStream(fileName)))) {
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while ((line = br.readLine()) != null) {
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// split by a comma separator
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String[] split = line.split(csvSeparator);
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System.out.println("\nLength : " + split.length);
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System.out.println("split[0] : " + split[0]);
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System.out.println("split[1] : " + split[1]);
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System.out.println("split[2] : " + split[2]);
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System.out.println("split[3] : " + split[3]);
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System.out.println("split[4] : " + split[4]);
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System.out.println("split[5] : " + split[5]);
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}
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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private static void readCSVFileReader() {
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String csvFile = "/Users/mkyong/csv/country.csv";
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String line;
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String csvSeparator = ",";
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// auto close file
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try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {
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while ((line = br.readLine()) != null) {
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// split by a comma separator
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String[] split = line.split(csvSeparator);
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System.out.println("\nLength : " + split.length);
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System.out.println("split[0] : " + split[0]);
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System.out.println("split[1] : " + split[1]);
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System.out.println("split[2] : " + split[2]);
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System.out.println("split[3] : " + split[3]);
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System.out.println("split[4] : " + split[4]);
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System.out.println("split[5] : " + split[5]);
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}
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}

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