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YogenRaiiYogenRaii
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Added example to read and write csv with opencsv
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‎pom.xml‎

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<artifactId>joda-time</artifactId>
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<version>2.9.9</version>
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</dependency>
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<!--opencsv-->
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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>4.0</version>
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</dependency>
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</dependencies>
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<repositories>

‎src/main/java/com/eprogrammerz/examples/csv/CsvReaderApplication.java‎

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package com.eprogrammerz.examples.csv;
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import java.util.List;
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import java.util.stream.Collectors;
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public class CsvReaderApplication {
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public static void main(String[] args) {
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processSensorData("input.csv");
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}
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public static void processSensorData(String fileName) {
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final CsvUtil csvUtil = new CsvUtil();
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// reading csv
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List<SensorRecord> sensorRecords = csvUtil.readCsvFile(fileName);
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if (sensorRecords == null) return;
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List<RecordStat> recordStats = sensorRecords
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.stream()
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.collect(Collectors.groupingBy(SensorRecord::getPlatformName, Collectors.averagingInt(SensorRecord::getReadingValue)))
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.entrySet().stream().map(e -> new RecordStat(e.getKey(), e.getValue())).collect(Collectors.toList());
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// write to csv
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csvUtil.writeStatsToCsv(recordStats);
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}
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}

‎src/main/java/com/eprogrammerz/examples/csv/CsvUtil.java‎

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package com.eprogrammerz.examples.csv;
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import com.opencsv.CSVWriter;
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import com.opencsv.bean.CsvToBean;
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import com.opencsv.bean.CsvToBeanBuilder;
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import com.opencsv.bean.StatefulBeanToCsv;
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import com.opencsv.bean.StatefulBeanToCsvBuilder;
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import com.opencsv.exceptions.CsvDataTypeMismatchException;
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import com.opencsv.exceptions.CsvRequiredFieldEmptyException;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import java.io.IOException;
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import java.io.Reader;
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import java.io.Writer;
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import java.net.URISyntaxException;
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import java.nio.file.Files;
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import java.nio.file.Paths;
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import java.util.List;
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/**
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* @author Yogen Rai
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*/
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public class CsvUtil {
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private static final Logger LOGGER = LoggerFactory.getLogger(CsvUtil.class);
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public static final String RESULT_FILE_NAME = "result.csv";
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public List<SensorRecord> readCsvFile(String fileName) {
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LOGGER.info("readCsvFile(): {}", fileName);
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try (Reader reader = Files.newBufferedReader(Paths.get(CsvUtil.class.getClassLoader()
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.getResource(fileName).toURI()))) {
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CsvToBean<SensorRecord> csvToBean = new CsvToBeanBuilder(reader)
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.withType(SensorRecord.class)
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.withIgnoreLeadingWhiteSpace(true)
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.build();
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return csvToBean.parse();
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} catch (URISyntaxException | IOException e) {
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LOGGER.warn("Error while reading csv . . .", e);
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}
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return null;
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}
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public void writeStatsToCsv(List<RecordStat> recordStats) {
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try (Writer writer = Files.newBufferedWriter(Paths.get(RESULT_FILE_NAME))) {
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StatefulBeanToCsv<RecordStat> beanToCsv = new StatefulBeanToCsvBuilder(writer)
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.withQuotechar(CSVWriter.NO_QUOTE_CHARACTER)
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.build();
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beanToCsv.write(recordStats);
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} catch (CsvDataTypeMismatchException | CsvRequiredFieldEmptyException | IOException e) {
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LOGGER.warn("Error while writing csv . . .", e);
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}
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}
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}

‎src/main/java/com/eprogrammerz/examples/csv/RecordStat.java‎

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package com.eprogrammerz.examples.csv;
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import com.opencsv.bean.CsvBindByPosition;
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/**
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* @author Yogen Rai
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*/
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public class RecordStat {
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@CsvBindByPosition(position = 0)
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private String platformName;
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@CsvBindByPosition(position = 1)
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private double weightedAvg;
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public RecordStat() {
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}
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public RecordStat(String platformName, double weightedAvg) {
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this.platformName = platformName;
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this.weightedAvg = weightedAvg;
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}
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public String getPlatformName() {
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return platformName;
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}
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public double getWeightedAvg() {
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return weightedAvg;
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}
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}

‎src/main/java/com/eprogrammerz/examples/csv/SensorRecord.java‎

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package com.eprogrammerz.examples.csv;
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import com.opencsv.bean.CsvBindByPosition;
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/**
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* @author Yogen Rai
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*/
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public class SensorRecord {
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@CsvBindByPosition(position = 0)
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private String platformName;
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@CsvBindByPosition(position = 1)
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private long sendTime;
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@CsvBindByPosition(position = 2)
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private long receiveTime;
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@CsvBindByPosition(position = 3)
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private int sensorNumber;
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@CsvBindByPosition(position = 4)
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private int readingValue;
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public SensorRecord() {
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}
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public SensorRecord(String platformName, long sendTime, long receiveTime, int sensorNumber, int readingValue) {
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this.platformName = platformName;
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this.sendTime = sendTime;
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this.receiveTime = receiveTime;
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this.sensorNumber = sensorNumber;
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this.readingValue = readingValue;
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}
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public String getPlatformName() {
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return platformName;
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}
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public long getSendTime() {
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return sendTime;
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}
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public long getReceiveTime() {
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return receiveTime;
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}
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public int getSensorNumber() {
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return sensorNumber;
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}
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public int getReadingValue() {
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return readingValue;
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}
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}

‎src/main/resources/input.csv‎

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P,1544988821,1544997821,4,418
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J,1544995905,1544998770,59,-829
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PY,1544992054,1544999135,70,215
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DVG,1544992753,1544999201,57,251
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PY,1544994083,1544999873,60,-457
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P,1544998137,1545000549,71,-599
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P,1544997920,1545000874,28,-233
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DVG,1544997165,1545001599,55,856
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PY,1544994398,1545001782,68,294
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P,1544993539,1545002661,23,609
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J,1544999206,1545003567,30,-422
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W,1545000779,1545003790,77,-831
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J,1544998749,1545004498,39,-642
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DVG,1545000248,1545004568,32,776
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PY,1545004202,1545005190,64,-671
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J,1544997131,1545006124,95,134

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