正在创建文件，但没有保存数据吗？

Question

我已经浏览了几个常见问题，并确保我关闭了文件，但没有保存任何数据。该文件是在文件系统中创建的，只是显示为空白。我的程序从另一个文件中提取数据并进行一些计算。然后，它将通过if语句发送数据，并在其中打印出新文件的必需内容。

import java.io.*;
import java.util.*;
public class Main {
    public static void main(String[] args) throws FileNotFoundException {

        int tempf, windspeed;
        Scanner x;

        try {
            x = new Scanner(new File("weatherData.txt"));
            PrintWriter out = new PrintWriter(new File("numbers.txt"));
            while (x.hasNextLine()) {
                String[] data = x.nextLine().split("\\s+"); // Split the line on space(s)

                try  {
                    tempf = Integer.parseInt(data[1]);
                    //System.out.print(tempf + " ");
                } catch (Exception e) {
                    System.out.println("Invalid/No data for temperature");
                    tempf = 0;
                }
                try {
                    windspeed = Integer.parseInt(data[2]);
                    //System.out.println(windspeed);
                } catch (Exception e) {
                    //System.out.println("NA");
                    windspeed = 0;
                }
                 double C1 = -42.379;
                 double C2 = 2.04901523;
                 double C3 = 10.14333127;
                 double C4 = -0.22475541;
                 double C5 = -.00683783;
                 double C6 = -5.481717E-2;
                 double C7 = 1.22874E-3;
                 double C8 = 8.5282E-4;
                 double C9 = -1.99E-6;
                 int celsius = ((tempf-32)*5/9); //Celcius equatin
                 double windmps = windspeed / 2.23694; // Wind in mps equation
                 double windchill = 35.74 + 0.6215*tempf + (0.4275*tempf - 35.75) * Math.pow(windspeed, 0.16); // Windchill equation 
                 double windchillc = ((windchill-32)*5/9);
                 double heatindexf =  C1 + (C2 * tempf) + (C3 * windspeed) + (C4 * tempf * windspeed) + (C5 * Math.pow(tempf,2) + (C6 * Math.pow(windspeed,2)) + (C7 * Math.pow(tempf,2) * windspeed) + (C8 * tempf * Math.pow(windspeed,2)) + (C9 * Math.pow(tempf,2) * Math.pow(windspeed,2)));
                 double heatindexc = ((heatindexf-32)*5/9);

                if (tempf <= 50) {

                    System.out.printf("%20s%20s%20s%20s%20s%20s\n", "Farenheit:","Celsius","Wind Speed(MPH)" ,"Wind Chill(F)" , "Wind Chill(C)" , "Wind Speed(MPS)");
                    System.out.printf("%20d%20d%20d%20d%20d%20d\n", tempf, celsius,windspeed ,(int)windchill, (int)windchillc, (int)windmps);

                }

                else if (tempf >= 80) {
                    System.out.printf("%20s%20s%20s%20s%20s\n", "Farenheit:","Celsius","Humidity %", "Heat Index(F)","Heat Index(C)");
                    System.out.printf("%20d%20d%20d%20d%20d\n", tempf ,celsius,windspeed , (int)heatindexf, (int)heatindexc);
                }

                else if (tempf > 50 && tempf < 80) {
                    System.out.printf("%20s%20s\n","Farenheit:","Celsius");
                    System.out.printf("%20d%20d\n",tempf,celsius);
                }
                out.close();
            }

        } catch (FileNotFoundException e) {
            System.out.println("Unable to read file.");
        }

    }
}

Answer 1

在循环内关闭后，您将无法写给作家。更改为：

PrintStream out = new PrintStream(new FileOutputStream("numbers.txt", true)); 
System.setOut(out);
while (x.hasNextLine()) {
    //Loop body

}

out.close();

也将文件更改为PrintStream，然后您可以直接将system.out打印内容写入文件。没有明确说明文件写入。

Answer 2

您已初始化PrintWriter，但未向其中写入任何内容。这就是文件内容为空的原因。将以下行添加到您的代码中，它将起作用。

System.out.printf（“％20s％20s％20s％20s％20s％20s \ n”，“ Farenheit：”，“ Celsius”，“风速（MPH）”，“风冷（F）”， “风寒（C）”，“风速（MPS）”）;

out.write（“％20s％20s％20s％20s％20s％20s \ n” +“” +“ Farenheit：” +“” +“ Celsius” +“” +“风速（MPH）” +“ “ +”风寒（F）“ +”“ +”风寒（C）“ +”“ +”风速（MPS）“）

out.flush（）;

这将起作用！！