無法在java中創建兩種單獨計算和讀取文件的方法

Question

嘗試創建兩種方法來計算no。的行和讀取文件的值，只有其中一個方法得到執行，另一個不執行，顯示以下錯誤：線程「主」java.lang.RuntimeException異常：java.io.IOException：讀取錯誤

請看下面的代碼：

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

只是一個小修改將做的工作：

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 
     } 


    } 

     } 

關閉所有其他流爲好。上面的代碼將爲你工作。乾杯。

Answer 2

當你關閉你的BufferedReader時，它也會關閉嵌套類，包括FileInputStream。

而不是關閉它，你應該嘗試並重置（）它重新開始讀它從一開始。

或者您必須重新打開FileInputStream。