Not able to create two methods for counting and reading a file individually in java

Question

When trying to create two methods for counting the no. of rows and reading the values of a file, only one of these methods got executed and another is not executed showing the following error :Exception in thread "main" java.lang.RuntimeException: java.io.IOException: Read error

Please look at the following code:

package com.ibm.csvreader;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;
import java.io.*;

public class CsvFileReader2  {

    public static class opencsvfile {

        HashMap <String , String> map= new HashMap <String, String> ();
        //csv file containing data
         // FileReader  strFile = new FileReader("C:/Users/vmuser/Desktop/SampleUpload.csv");
          //create BufferedReader to read csv file

         // BufferedReader br = new BufferedReader((strFile));
          String strLine = "";
          int lineNumber ; 
         public void  countrows(FileInputStream fstream) throws Exception{
             DataInputStream strFile  = new DataInputStream(fstream);
             BufferedReader br = new BufferedReader( new InputStreamReader (strFile));
              lineNumber =0;
             while( (strLine = br.readLine()) != null) {
                  lineNumber++;
                }
             System.out.println("no.of rows are :" +lineNumber);
             br.close();
         }
             public void readfile(FileInputStream fstream) throws Exception{
                 DataInputStream strFile  = new DataInputStream(fstream);
                 BufferedReader br = new BufferedReader( new InputStreamReader (strFile));
                 lineNumber =0;
                 while( (strLine = br.readLine()) != null) {
                      lineNumber++;
                      String[] tokens = strLine.split(","); 
                      String key = tokens[0].trim(); 
                      String nodes = tokens[1].trim(); 
                      map.put(key, nodes);

                             }
                 System.out.println("map is" + map );
                 br.close();
                  System.out.println("File is Closed");
         }
    }
    public static void main(String[] args) throws IOException {
        File fl = new File ("C:/Users/vmuser/Desktop/SampleUpload.csv");
        FileInputStream fstream = new FileInputStream(fl);

         opencsvfile f=new opencsvfile();
         try {
            f.countrows(fstream);

             f.readfile(fstream);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }


    }

         }

Answer 1

Just a small modification will do the work:

package com.ibm.csvreader;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;
import java.io.*;

public class CsvFileReader2  {



   public static class opencsvfile {

        HashMap <String , String> map= new HashMap <String, String> ();
        //csv file containing data
         // FileReader  strFile = new FileReader("C:/Users/vmuser/Desktop/SampleUpload.csv");
          //create BufferedReader to read csv file

         // BufferedReader br = new BufferedReader((strFile));
          String strLine = "";
          int lineNumber ; 
         public void  countrows(FileInputStream fstream) throws Exception{
             DataInputStream strFile  = new DataInputStream(fstream);
             BufferedReader br = new BufferedReader( new InputStreamReader (strFile));
              lineNumber =0;
             while( (strLine = br.readLine()) != null) {
                  lineNumber++;
                }
             System.out.println("no.of rows are :" +lineNumber);
             br.close();
         }
             public void readfile(FileInputStream fstream) throws Exception{
                 DataInputStream strFile  = new DataInputStream(fstream);
                 BufferedReader br = new BufferedReader( new InputStreamReader (strFile));
                 lineNumber =0;
                 while( (strLine = br.readLine()) != null) {
                      lineNumber++;
                      String[] tokens = strLine.split(","); 
                      String key = tokens[0].trim(); 
                      String nodes = tokens[1].trim(); 
                      map.put(key, nodes);

                             }
                 System.out.println("map is" + map );
                 br.close();
                  System.out.println("File is Closed");
         }
    }
    public static void main(String[] args) throws IOException {
        File fl = new File ("C:/Users/vmuser/Desktop/SampleUpload.csv");
        FileInputStream fstream = new FileInputStream(fl);

         opencsvfile f=new opencsvfile();
         try {
            f.countrows(fstream);

           fstream = new FileInputStream(fl);//include this line

             f.readfile(fstream);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
       finally{
          if(fstream!=null)
                fstream.close();//be sure to close all streams at last
      }


    }

         }

Close all other streams as well. Above code will work for you.Cheers.

Answer 2

When you close your BufferedReader, it also closes the nested classes, including the FileInputStream.

Instead of closing it, you should try and reset() it to restart reading it from the start.

Or you must re-open the FileInputStream.