Question

我正在尝试编写一个方法，如果一个“log.txt文件”尚未存在，则会生成“log.txt文件”然后写入该文件。我遇到的问题是每次调用该方法时，它都会覆盖现有的日志。如何更改方法，以便不是覆盖数据而只是更新文件？

我的写文件方法：

    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

只需将PrintWriter out = new PrintWriter(log);更改为

即可

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

Answer 2

改为使用FileWriter。

FileWriter(File file, boolean append)

构造函数中的第二个参数告诉FileWriter将任何给定的输入附加到文件而不是覆盖它。

这是您的示例的一些代码：

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

出于某种原因，其他方法都没有为我工作......所以我尝试了这个并且工作了。希望它有所帮助..

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

这是一个简单的例子，它是如何工作的，最好的做法是将try \ catch放入其中但是对于基本用途，这应该可以解决问题。为此，您有一个字符串和文件路径，因此适用于FileWriter和BufferedWriter。这将写入“Hello World”（数据变量），然后创建一个新行。每次运行时，它都会将Data变量添加到下一行。

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 6

尝试这个

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 7

您甚至可以使用FileOutputStream来获得所需内容。这就是它的完成方式，

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 8

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

如果要在一行中创建文件，

就是一个例子。

Answer 9

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

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

写入文本文件而不用Java覆盖

9 个答案: