Question

尝试编写java代码来编写“.dat”文件..同时拧紧检查大小...每200 KB创建新的“.dat”继续写入文件。有什么方法可以做到这一点..

当文件超过200KB并创建一个像这样的新文件名时

1st file name.. 1_filename 
2nd file name.. 2_filename
3rd file name.. 3_filename........

或者如果文件只创建一个文件意味着小于200KB而不是

Filenamd .. filename，如代码..

我写代码来编写文件，但是......它只写了2个文件..而且这不是正确的方法..

这是我的代码..

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;

public class xmlfile1filebytes {
    public static void main(String[] args) throws IOException {
        File folder = new File ("07072013");
        File[] listOfFiles = folder.listFiles();

        System.out.println("There are " + listOfFiles.length + " files"); 
        String filesin;

        String timeStamp = new SimpleDateFormat("MM-dd-yyyy[HH.mm.ss]")
        .format(Calendar.getInstance().getTime());
        System.out.println(timeStamp);

        BufferedWriter xmlfile = null;
        BufferedWriter datfile = null;

        String outxmlfile = ("07072013\\" + timeStamp + ".xml");
        xmlfile = new BufferedWriter(new FileWriter(outxmlfile));

        String outdatfile = ("07072013\\" + timeStamp + ".dat");
        datfile = new BufferedWriter(new FileWriter(outdatfile));

        int offset = 0;
        int size = 0;

        for (int i = 0; i < listOfFiles.length; i++) {
            File f = listOfFiles[i];
            // System.out.println(i + " " + f.getAbsolutePath());
            if (f.isFile()) {
                filesin = listOfFiles[i].getName();
                if (filesin.endsWith("pdf")) {
                    Path aPath = Paths.get(f.getAbsolutePath()); 
                    System.out.println(filesin);
                    byte[] actualBytes = Files.readAllBytes(aPath);
                    size = actualBytes.length;
                    xmlfile.append((i + 1) + ")" + " File = " + filesin + ", Offset = " + offset + ", Size = " + size + "\n");

                    offset = offset + size;
                    xmlfile.newLine();

                    String s = new String(actualBytes);

                    datfile.append(s);
                    datfile.newLine();

                    File datfileinfolder = new File ("07072013\\" + timeStamp + ".dat");

                    long datfilesize = datfileinfolder.length();
                    long datfilesizeinkb = datfilesize /1024;

                    System.out.println(datfilesizeinkb);

                    if (datfilesizeinkb >= 200) {
                        datfile.close();

                        BufferedWriter datfile1 = null;
                        String outdatfile1 = ("07072013\\" + "1_"+ timeStamp + ".dat");
                        datfile1 = new BufferedWriter(new FileWriter(outdatfile1));

                        String s1 = new String(actualBytes);
                        datfile1.append(s1);
                        datfile1.close();
                    }
                }
            }
        }
        xmlfile.close();
    }
}

当写入文件超过400 KB时我收到错误..

ERROR：

    There are 10 files
07-09-2013[16.03.00]
1192970_eBill_20130709.pdf
96
1321470_eBill_20130709.pdf
208
1724897_eBill_20130709.pdf
Exception in thread "main" java.io.IOException: Stream closed
    at java.io.BufferedWriter.ensureOpen(Unknown Source)
    at java.io.BufferedWriter.write(Unknown Source)
    at java.io.Writer.write(Unknown Source)
    at java.io.Writer.append(Unknown Source)
    at xmlfile1filebytes.main(xmlfile1filebytes.java:65)

Answer 1

我建议您创建一个单独的类，其唯一的工作是创建文件（按顺序），将数据写入文件，密切关注大小，并根据需要关闭/打开文件。这将使您的代码更有条理 - 您将能够更清楚地看到您的错误。该课程将具有以下方法：

setMax(maxVal)                 - set the maximum file size (default 400k)
setRoot(rootPath)              - folder where files will be created
setName(rootName)              - "format string" used to generate file names 
                                 (e.g. "myFile%03d.dat")
writeData(dataSize, dataBlock) - write data. If no file open, open it. 
                                 If file too big, split it.  
closeFile()                    - flush buffers, close the last file.
                                 Could be part of the destructor
currentFile()                  - returns name of current file (for debug)
currentSize()                  - returns current file size (for debug)

如果你能弄清楚如何编写这个课程，你将解决你的初始问题，并有一些你可以同时重复使用的东西。

如果您希望（大部分）保留您已有的代码结构，那么您的修复就是删除当前行85.

     83:         String s1 = new String(actualBytes);
     84:         datfile1.append(s1);
     85:         datfile1.close();  <<<<<<<<<<< remove this line
     86:      }

关闭文件后，下次尝试写入文件将失败 - 这就是您所看到的错误。

Answer 2

你做datfile.close()，并在下一次迭代中通过for循环你.append()。您必须在for循环内初始化（即打开）。

Answer 3

好吧看起来像是一本书存问题。

以下是它应该是什么样子

    .
    .
    . 
    long datfilesize = datfileinfolder.length();;
    final int BLOCK_SIZE = 200 * 1024;
    for (int curBlock = 0; curBlock < actualBytes.length; curBlock += BLOCK_SIZE) {
        String toWrite = new String(
            Arrays.copyOfRange(actualBytes, curBlock, Math.min(curBlock + BLOCK_SIZE, actualBytes.length)
        );
        String suffix = "";
        if (curBlock > 0) {
            //append underscores other file information and then perform writes
            suffix =  String.valueOf(curBlock /  BLOCK_SIZE);
        }    

        //Your code more or less
        BufferedWriter datfile1 = null;
        String outdatfile1 = ("07072013\\" + suffix + timeStamp + ".dat");
        datfile1 = new BufferedWriter(new FileWriter(outdatfile1));


        datfile1.append(toWrite);
        datfile1.close(); 
    }

编辑：这更有意义吗？

这是要点。 for循环以块大小BLOCK_SIZE（200 KB）进行迭代。如果文件大小小于BLOCK_SIZE，则无需附加任何后缀（请参阅 if block ）。否则，您附加后缀，然后写入该文件。字符串由局部变量 toWrite 给出。您已经读取了整个文件并将字节存储在 actualBytes 中。希望这更有意义。

Java自动创建新文件取决于大小

3 个答案: