爪哇.如何将文本附加到 file.txt 的顶部 [英] Java. How to append text to top of file.txt

问题描述

我需要通过 Java 在文本文件的开头添加文本.

I need to add text to beggining of text file via Java.

例如我有包含数据的 test.txt 文件:

For example I have test.txt file with data:

Peter
John
Alice

我需要添加(到文件顶部):

I need to add(to top of file):

Jennifer 

应该是:

Jennifer
Peter
John
Alice

我有一部分代码，但是它将数据附加到文件末尾，我需要让它在文件顶部添加文本:

I have part of code, but It append data to end of file, I need to make It that added text to top of file:

    public static void irasymas(String irasymai){
        try {
         File file = new File("src/lt/test.txt");

                if (!file.exists()) {
                file.createNewFile();
            }

            FileWriter fw = new FileWriter(file.getAbsoluteFile(), true);
            BufferedWriter bw = new BufferedWriter(fw);
            bw.write(irasymai+ "\r\n");
            bw.close();
} 
       catch (IOException e) {
        e.printStackTrace();                
        }
    }

我已经试过了，但这只会从文件中删除所有数据，而不是插入任何文本:

I have tried this, but this only deletes all data from file and not insert any text:

public static void main(String[] args) throws IOException {
        BufferedReader reader = null;
        BufferedWriter writer = null;
        ArrayList list = new ArrayList();

        try {
            reader = new BufferedReader(new FileReader("src/lt/test.txt"));
            String tmp;
            while ((tmp = reader.readLine()) != null)
                list.add(tmp);
            OUtil.closeReader(reader);

            list.add(0, "Start Text");
            list.add("End Text");

            writer = new BufferedWriter(new FileWriter("src/lt/test.txt"));
            for (int i = 0; i < list.size(); i++)
                writer.write(list.get(i) + "\r\n");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            OUtil.closeReader(reader);
            OUtil.closeWriter(writer);
        }
    }

感谢您的帮助.

推荐答案

您可以使用 RandomAccessFile 使用seek(long position)方法将光标seek到0th位置，在开始写作之前.

You can use RandomAccessFile to and seek the cursor to 0th position using seek(long position) method, before starting to write.

如中所述这个线程

RandomAccessFile f = new RandomAccessFile(new File("yourFile.txt"), "rw");
f.seek(0); // to the beginning
f.write("Jennifer".getBytes());
f.close();

正如下面许多评论所指出的，这个解决方案从一开始就覆盖文件内容.要完全替换内容，可能需要删除和重写文件.

As pointed out below by many comments, this solution overwrites the file content from beginning. To completely replace the content, the File may have to be deleted and re-written.

这篇关于爪哇.如何将文本附加到 file.txt 的顶部的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！