写入文本文件而不用Java覆盖

Question

I am trying to write a method that makes a "log.txt file" if one does not already exist and then writes to the file. The problem that I am encountering is every time I call the method, it overwrites the existing log. How do I change the method so that instead of overwriting the data it just updates the file?

My Write File Method:

    File log = new File("log.txt")
    try{
    if(log.exists()==false){
            System.out.println("We had to make a new file.");
            log.createNewFile();
    }
    PrintWriter out = new PrintWriter(log);
    out.append("******* " + timeStamp.toString() +"******* " + "\n");
    out.close();
    }catch(IOException e){
        System.out.println("COULD NOT LOG!!");
    }

Answer 1

Just change PrintWriter out = new PrintWriter(log); to

PrintWriter out = new PrintWriter(new FileWriter(log, true));

Answer 2

use a FileWriter instead.

FileWriter(File file, boolean append)

the second argument in the constructor tells the FileWriter to append any given input to the file rather than overwriting it.

here is some code for your example:

File log = new File("log.txt")

try{
    if(!log.exists()){
        System.out.println("We had to make a new file.");
        log.createNewFile();
    }

    FileWriter fileWriter = new FileWriter(log, true);

    BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
    bufferedWriter.write("******* " + timeStamp.toString() +"******* " + "\n");
    bufferedWriter.close();

    System.out.println("Done");
} catch(IOException e) {
    System.out.println("COULD NOT LOG!!");
}

Answer 3

For some reason, none of the other methods worked for me...So i tried this and worked. Hope it helps..

JFileChooser c= new JFileChooser();
c.showOpenDialog(c);
File write_file = c.getSelectedFile();
String Content = "Writing into file\n hi \n hello \n hola";
try 
{
    RandomAccessFile raf = new RandomAccessFile(write_file, "rw");
    long length = raf.length();
    System.out.println(length);
    raf.setLength(length + 1); //+ (integer value) for spacing
    raf.seek(raf.length());
    raf.writeBytes(Content);
    raf.close();
} 
catch (Exception e) {
    System.out.println(e);
}

Answer 4

JFileChooser c= new JFileChooser();
c.showOpenDialog(c);
File write_file = c.getSelectedFile();
String Content = "put here the data to be wriiten";
try
    {
    FileWriter fw = new FileWriter(write_file);
    BufferedWriter bw = new BufferedWriter(fw);
    bw.append(Content);
    bw.append("hiiiii");
    bw.close();
    fw.close();
    }
catch(Exception e)
   {
    System.out.println(e);
   `}

Answer 5

You can even use FileOutputStream to get what you need. This is how it can be done,

File file = new File(Environment.getExternalStorageDirectory(), "abc.txt");
FileOutputStream fOut = new FileOutputStream(file, true);
OutputStreamWriter osw = new OutputStreamWriter(fOut);
osw.write("whatever you need to write");
osw.flush();
osw.close();

Answer 6

您可以更改 PrintWriter 并使用 getAbsoluteFile() 方法，此函数返回给定抽象路径名的绝对 File 对象。

PrintWriter out = new PrintWriter(new FileWriter(log.getAbsoluteFile(), true));

Answer 7

try this one

 public void writeFile(String arg1,String arg2) { try { if (!dir.exists()) { if (dir.mkdirs()) { Toast.makeText(getBaseContext(), "Directory created", Toast.LENGTH_SHORT).show(); } else { Toast.makeText(getBaseContext(), "Error writng file " + filename, Toast.LENGTH_LONG) .show(); } } else { File file = new File(dir, filename); if (!file.exists()) { file.createNewFile(); } FileWriter fileWritter = new FileWriter(file, true); BufferedWriter bufferWritter = new BufferedWriter(fileWritter); bufferWritter.write(arg1 + "\\n"); bufferWritter.close(); } catch (Exception e) { e.printStackTrace(); Toast.makeText(getBaseContext(), "Error writng file " + e.toString(), Toast.LENGTH_LONG) .show(); } }

Answer 8

Here is a simple example of how it works, best practice to put a try\\catch into it but for basic use this should do the trick. For this you have a string and file path and apply thus to the FileWriter and the BufferedWriter. This will write "Hello World"(Data variable) and then make a new line. each time this is run it will add the Data variable to the next line.

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;


String Data = "Hello World";
File file = new File("C:/Users/stuff.txt");
FileWriter fw = new FileWriter(file,true);
BufferedWriter bw = new BufferedWriter(fw);
bw.write(Data);
bw.newLine();
bw.close();

Answer 9

BufferedWriter login = new BufferedWriter(new FileWriter("login.txt"));

如果您想在一行中创建一个文件，这是一个示例。