Question

我还是java新手，只有一个学期。我有第一次实习，这不是一个编程实习，只是一般的IT实习，因为这只是我的第一个学期。我的老板不懂Java，大楼里也没有人知道。他知道我有一些基本的编程经验，并告诉我要解决他遇到的问题。他有一个保存的报告和最后一行，报告的最后一个字符是字符转弯符号，我们需要删除它，因为它在网站上给我们带来了问题。我不确定我是否在正确的轨道上，此时我只是在试错。请帮忙：D

 public class RemoveChar {

    public static void main(String[] args) throws FileNotFoundException {

    // Variables and stuff
    Scanner keyScan = new Scanner(System.in);
    JFrame frameOne = new JFrame ("File Name");
    Scanner fileScan = new Scanner(System.in);
    String fileName;

    // Ask user for file name
    System.out.print("What is the file full file name? ");
    fileName = fileScan.nextLine();

    // Add .txt if the user forgets to put it in the prompt
    if (!fileName.contains(".txt"))
        fileName += ".txt";

    //Test to see if file exists
    File myFile = new File(fileName);
    if(!myFile.exists()){
        System.out.println(fileName + " does not exist. ");
        System.exit(0);
    }

    fWriter = new FileWriter("config/lastWindow.txt", true);
    /*while(fileName.hasNext()){

    }
    File 
    BufferedReader inputFile = new BufferedReader(new FileReader("C:\\" +        fileScan));
    //Scanner reader = new Scanner (inputFile);
    */



  }

}

Answer 1

文件有多大？如果它们不是那么大，你可以将整个文件读成一个字符串然后砍掉最后一个字符：

//Set delimiter to end-of-string anchor \Z so that you can read the
//file in with just one call to next()
//from: http://stackoverflow.com/a/3403112/263004

String content = new Scanner(new File("filename")).useDelimiter("\\Z").next();
String withoutLastCharacter = content.substring(0, content.length - 1);

然后你只需要将withoutLastCharacter写到文件中。

否则，您需要逐行读取原始文件并将其写入临时文件，然后将该文件复制到原始文件上。但是，如果你在最后一行，你将砍掉最后一个字符。这里有一些代码可以让您了解基本逻辑：

while(scanner.hasNextLine()) {
    String line = scanner.nextLine();

    //If this is the last line chop off the last character.
    if(!scanner.hasNextLine()) {
        line = line.substring(0, line.length - 1);
    }

    //Write line out to temporary file
    ...
}

您还提到它不一定是Java。如果您使用的是Linux或Mac，则可以使用sed：

执行此操作

sed -i '$s/.$//' <filename>

这将删除文件的最后一行的最后一个字符。

Answer 2

这是否必须是java问题？对于像这样的基本文件/字符串操作，我更喜欢使用像Perl这样的东西。下面的perl脚本将从文件中删除最后一个字节（或本例中为char）

    my $fsize = -s $filename;  
    # print $size."\n";
    open($FILE, "+<", $filename) or die $!; 
    seek $FILE, $size-2, SEEK_SET; 
    print $FILE ";";

    close $FILE;

Answer 3

 static class CopyFileContent {

    public static void main(String[] args) {

        String root = Environment.getExternalStorageDirectory().toString(); //get access to directory path
        File myDir = new File(root + "/MyFolder");//create folder in internal storage
        myDir.mkdirs();// make directory
        File destFile = new File(myDir, FILENAME11);//making a new file in the folder
    /* Source file, from which content will be copied */
        File sourceFile1 = new File(myDir, FILENAME12);
        File sourceFile2 = new File(myDir, FILENAME13);
        File sourceFile3 = new File(myDir, FILENAME14);

    /* destination file, where the content to be pasted */
        // File destFile = new File(FILENAME);

    /* if file not exist then create one */
        if (!destFile.exists()) {
            try {
                destFile.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        InputStream input1 = null;
        InputStream input2 = null;
        InputStream input3 = null;
        OutputStream output = null;
        InputStream input4 = null;

        try {

        /* FileInputStream to read streams */
            input1 = new FileInputStream(sourceFile1);
            input2 = new FileInputStream(sourceFile2);
            input3 = new FileInputStream(sourceFile3);

        /* FileOutputStream to write streams */
            output = new FileOutputStream(destFile, true);

            byte[] buf = new byte[1024];
            int bytesRead;
            output.write("{Record:[{".getBytes());
            while ((bytesRead = input1.read(buf)) > 0) {
                output.write(buf, 1, bytesRead);

                RandomAccessFile f = new RandomAccessFile(destFile, "rw");
                long length = f.length() - 2;
                f.setLength(length);
                length = f.length();
                f.close();
                output.write(",".getBytes());

            }

            while ((bytesRead = input2.read(buf)) > 0) {
                output.write(buf, 1, bytesRead);
                RandomAccessFile f = new RandomAccessFile(destFile, "rw");
                long length = f.length() - 2;
                f.setLength(length);
                length = f.length();
                f.close();
                output.write(",".getBytes());

            }

            while ((bytesRead = input3.read(buf)) > 0) {
                output.write(buf, 1, bytesRead);
                RandomAccessFile f = new RandomAccessFile(destFile, "rw");
                long length = f.length() - 2;
                f.setLength(length);
                length = f.length();
                f.close();
                output.write(",".getBytes());
                output.write(b.getBytes());
                output.write(d.getBytes());
                output.write("}]}".getBytes());

                output.write("\r\n".getBytes());

            }
        RandomAccessFile f1=new RandomAccessFile(destFile,"rw");
            long length1= f1.length()-1;
                f1.setLength(length1);
                f1.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {

                if (null != input1) {
                    input1.close();
                }

                if (null != input2) {
                    input2.close();
                }

                if (null != input3) {
                    input3.close();
                }

                if (null != output) {
                    output.close();
                }

            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }

}

JAVA Help：附加文件并删除最后一个字符

3 个答案: