Reading CSV File Using JAVA

Sometime we need to parse CSV(Comma Separated Values) file for data reading or writing .We use CSV file due to platform independence .There are lots of API available to parse a CSV file but here we use simple JAVA code, later we will learn how to use JAVA API for reading and writing a CSV file.

STEP 1 :
 Basically we need this lines to read a file.
try (InputStream fileStream = new BufferedInputStream(new FileInputStream(filePath));

STEP 2 :
 To read a file with different character set except English then we need to support for UTF-8 characters.So we use Reader class for that.
     Reader ir = new InputStreamReader(fileStream, "UTF-8");

STEP 3 :
  Now we create a BufferedReader object to read a file in a speedy way.
     BufferedReader buffReader = new BufferedReader(ir));

STEP 4 :
  We use readLine() method on BufferedReader object and loop will iterate until this object will be null.
              while ((line = buffReader.readLine()) != null) {
                csvData = line.split(separator);
                list.add(csvData);
            }  


 Example Code :

package csvfilehandling;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class CSVReadingWithOutAPI {

    public static void main(String[] args) {
        try {
            //System.out.println((getCSVInList("Our CSV File Path", ",").get(0))[1]);
            for (String[] csvDataRow : getCSVInList("Our CSV File Path", ",")) {
                for (String csvDataOnColumn : csvDataRow) {
                    System.out.println(csvDataOnColumn);
                }
            }
            //System.out.println(getCSVInMap("Our CSV File Path", ",").get(0).get(1));
            for (Map.Entry<Integer, List<String>> csvDataSet : getCSVInMap("Our CSV File Path", ",").entrySet()) {
                for (String csvData: csvDataSet.getValue()) {
                    System.out.println(csvData);
                }
            }
            //System.out.println(getCSVFromColumn("Our CSV File Path", ",", "DATACOLUMN1"));
            for (String columndata : getCSVFromColumn("Our CSV File Path", ",", "DATACOLUMN1")) {
                System.out.println(columndata);
            }
        } catch (IOException ex) {
            System.out.println(ex.getMessage());
        }
    }

    public static List<String[]> getCSVInList(String filePath, String separator) throws IOException {
        List<String[]> list = new ArrayList<>();
        /**
         * We use try-with-resources Statement for close the resource and
         * release it .
         */
try (InputStream fileStream = new BufferedInputStream(new FileInputStream(filePath));
                Reader ir = new InputStreamReader(fileStream, "UTF-8");
                BufferedReader buffReader = new BufferedReader(ir)) {
            String line;
            String[] csvData;
            while ((line = buffReader.readLine()) != null) {
                csvData = line.split(separator);
                list.add(csvData);
            }
        }
        return list;
    }

    public static Map<Integer, List<String>> getCSVInMap(String filePath, String separator) throws IOException {
        Map<Integer, List<String>> map = new HashMap<>();
        /**
         * We use try-with-resources Statement for close the resource and
         * release it .
         */
try (InputStream fileStream = new BufferedInputStream(new FileInputStream(filePath));
                Reader ir = new InputStreamReader(fileStream, "UTF-8");
                BufferedReader buffReader = new BufferedReader(ir)) {
            String line;
            String[] csvData;
            int lineNumber = 0;
            while ((line = buffReader.readLine()) != null) {
                csvData = line.split(separator);
                map.put(lineNumber, Arrays.asList(csvData));
                lineNumber++;
            }
        }
        return map;
    }

    public static List<String> getCSVFromColumn(String filePath, String separator, String columnName) throws IOException {
        List<String> columnList = new ArrayList<>();
        /**
         * We use try-with-resources Statement for close the resource and
         * release it .
         */
try (InputStream fileStream = new BufferedInputStream(new FileInputStream(filePath));
                Reader ir = new InputStreamReader(fileStream, "UTF-8");
                BufferedReader buffReader = new BufferedReader(ir)) {
            String line;
            String[] csvDataInCurrentLine;
            int lineNumber = 0;
            int columnNumber = 0;
            while ((line = buffReader.readLine()) != null) {
                csvDataInCurrentLine = line.split(separator);
                /**
                 * This is a one time checking for First Line Reading .
                 */
                if (lineNumber == 0) {
                    /**
                     * Use binarySearch to find the column name from String
                     * Array String[] csvDataInCurrentLine; .
                     */
                    if (Arrays.binarySearch(csvDataInCurrentLine, columnName) < 0) {
                        break;
                    }
                    columnNumber = Arrays.asList(csvDataInCurrentLine).indexOf(columnName);
                } else {
                    columnList.add(csvDataInCurrentLine[columnNumber]);
                }
                lineNumber++;
            }
        }
        return columnList;
    }
}