java 添加新行到 txt\log 文件

Question

我正在尝试为我的 java 脚本创建一个日志文件，以节省设备启动时的时间。

它正在工作 - 每次启动他都会在文件中节省我的时间但我想每次启动时添加一个新行，现在它会覆盖该文件所以文件总是 1 行(最后一次启动时)

我需要改变什么？

这是我编写的代码:

import java.io.*;
import java.net.*;
import java.util.*;
import java.util.Calendar;
import java.util.concurrent.TimeUnit;
import java.text.SimpleDateFormat;
import java.util.Scanner;

public class HelloWorld {
    public static void main(String[] args) throws Exception 
    {

        Writer output; //to write the data into a file 
        String PathOfFile = "/home/pi/boot.log";
        PrintWriter writer = new PrintWriter(PathOfFile);
        output = new BufferedWriter(new FileWriter(PathOfFile , true));
        Calendar Time = Calendar.getInstance(); //get the time 
        SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy-HH:mm:ss");

        try 
        {
            System.out.println("Hello - the device is UP and running now :-)");

            output.append ("\r\n" + sdf.format(Time.getTime()) + "   Unit is UP\r\n " );
            output.close();

            System.exit(0);
        }

        catch (Exception e)
        {
            System.err.println(e);
            output.append (sdf.format(Time.getTime()) +  "    " + e );
            output.close();

        }
    }

}

Answer 1

PrintWriter的方法被称为append()并不意味着它改变了正在打开的文件的模式。

您还需要以追加模式打开文件:

此外，您没有在代码中使用 printwriter，因此可以将其删除。试试这个

import java.io.*;
import java.net.*;
import java.util.*;
import java.util.Calendar;
import java.util.concurrent.TimeUnit;
import java.text.SimpleDateFormat;
import java.util.Scanner;

public class HelloWorld {
    public static void main(String[] args) throws Exception 
    {

        Writer output; //to write the data into a file 
        String PathOfFile = "/home/pi/boot.log";
        //PrintWriter writer = new PrintWriter(PathOfFile , true /* append = true */)
        output = new BufferedWriter(new FileWriter(PathOfFile , true));
        Calendar Time = Calendar.getInstance(); //get the time 
        SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy-HH:mm:ss");
        try 
        {
            System.out.println("Hello - the device is UP and running now :-)");
            output.append ("\r\n" + sdf.format(Time.getTime()) + "   Unit is UP\r\n " );
            output.close();

            System.exit(0);
        }

        catch (Exception e)
        {
            System.err.println(e);
            output.append (sdf.format(Time.getTime()) +  "    " + e );
            output.close();
        }
    }
}