BufferedWriter不会将所有内容写入输出文件 [英] BufferedWriter not writing everything to its output file

问题描述

我有一个Java程序，从文件中逐行读取一些文本，并将新文本写入输出文件。但是，在程序结束后，输出文件中并没有写入我的 BufferedWriter 的所有文本。为什么会这样？

详细信息：该程序将一个CSV文本文档转换为SQL命令以将数据插入到表中。该文本文件有超过10000行，看起来类似于以下内容：

$ pre code> 2007,10,9,1,1,1006134， 19423882

该程序似乎工作正常，除了它只是停止在文件随机创建一个新的一半已将SQL语句打印到SQL文件中。它看起来像这样：

  insert into nyccrash values（2007，1，2，1，4，1033092，259916）; 
插入nyccrash值（2007,1,1,1,1,1020246,197687）; 
插入到nyccrash值（2007,10,9,1 
  

大约10000但在文件结尾处有几百行，发生中断的地方在 1 和之间，之间。然而，这些字符似乎并不重要，因为如果我将 1 更改为 42 ，最后写入新文件是 4 ，这是从该整数中删除2，所以看起来读者或写作者在写入/读取一定量之后必定会死亡。我的Java代码如下：

  import java.io. * ; 
 
 public class InsertCrashData 
 {
 public static void main（String args []）
 {
 try 
 {
 //打开输入文件
 FileReader istream = new FileReader（nyccrash.txt）; 
 BufferedReader in = new BufferedReader（istream）; 
 //打开输出t文件。 
 FileWriter ostream = new FileWriter（nyccrash.sql）; 
 BufferedWriter out = new BufferedWriter（ostream）; 
字符串行，sqlstr; 
 
 sqlstr =CREATE TABLE nyccrash（crash_year integer，accident_type integer，collision_type integer，weather_condition integer，light_condition integer，x_coordinate integer，y_coordinate integer）; \\\
\\\
; 
 out.write（sqlstr）; （（line = in.readLine（））！= null）
 
 
 
 String [] esa = line.split（，）; 
 sqlstr =insert into nyccrash values（+ esa [0] +，+ esa [1] +，+ esa [2] +，+ esa [3] +， esa [4] +，+ esa [5] +，+ esa [6] +）; \\\
; 
 out.write（sqlstr）; 
 
 
 catch（Exception e）
 {
 System.out.println（e）; 
 
 
 
 
 $ div class =h2_lin>解决方案

您需要关闭 OutputStream ，这将清空您的数据的其余部分：



  out.close（）; 
  

BufferedWriter 的默认缓冲区大小为< a href =http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/io/BufferedWriter.java#BufferedWriter.0defaultCharBufferSize> 8192个字符，足够容易保存数百行未写入的数据。

I have a Java program that reads some text from a file, line by line, and writes new text to an output file. But not all the text I write to my BufferedWriter appears in the output file after the program has finished. Why is that?

The details: the program takes a CSV text document and converts it into SQL commands to insert the data into a table. The text file has more than 10000 lines which look similar to following:

2007,10,9,1,1,1006134,19423882

The program seems to work fine except it just stops in the file randomly half way through creating a new SQL statement having printed it into the SQL file. It looks something like:

insert into nyccrash values (2007, 1, 2, 1, 4, 1033092, 259916);
insert into nyccrash values (2007, 1, 1, 1, 1, 1020246, 197687);
insert into nyccrash values (2007, 10, 9, 1

This happens after about 10000 lines but several hundred lines before the end of the file. Where the break happens is between a 1 and a ,. However, the characters doesn't seem important because if I change the 1 to a 42 the last thing written to the new file is 4, which is cutting off the 2 from that integer. So it seems like the reader or writer must just be dying after writing/reading a certain amount.

My Java code is as follows:

import java.io.*;

public class InsertCrashData
{
    public static void main (String args[])
    {
        try
        {   
            //Open the input file.
            FileReader istream = new FileReader("nyccrash.txt");
            BufferedReader in = new BufferedReader(istream);
            //Open the output file.
            FileWriter ostream = new FileWriter("nyccrash.sql");
            BufferedWriter out = new BufferedWriter(ostream);
            String line, sqlstr;

            sqlstr = "CREATE TABLE nyccrash (crash_year integer, accident_type integer, collision_type integer, weather_condition integer, light_condition integer, x_coordinate integer, y_coordinate integer);\n\n"; 
            out.write(sqlstr);

            while((line = in.readLine())!= null)
            {
                String[] esa = line.split(",");
                sqlstr = "insert into nyccrash values ("+esa[0]+", "+esa[1]+", "+esa[2]+", "+esa[3]+", "+esa[4]+", "+esa[5]+", "+esa[6]+");\n";
                out.write(sqlstr);
            }
        }
        catch(Exception e)
        {
            System.out.println(e);
        }
    }
}

解决方案

You need to close your OutputStream which will flush the remainder of your data:

out.close();

The default buffer size for BufferedWriter is 8192 characters, large enough to easily hold hundreds of lines of unwritten data.

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