将已完成程序（在控制台上）的结果打印到文本文件？

Question

我是 Java 的新手，如果有任何不清楚的地方，我深表歉意 - 我也想将控制台上的内容打印到文本文件中 - 但我只希望它打印到文件在最后 - 所以基本上它会运行通过所有程序（这是一个猜谜游戏），然后一旦完成，它会要求用户输入文件名，然后将控制台上的内容打印到那个文件。我对 PrintWriter 和 BufferedWriter 等有点熟悉，但是当我想打印出控制台上存在的结果时，我不确定该怎么做，如下所示（问题是 system.out.print 和数字 3、18 , 19 是用户输入）。任何帮助将不胜感激！

Please guess a number between 1 and 20: 3

Too low, try again. Please guess a number between 1 and 20: 18

Too low, try again. Please guess a number between 1 and 20: 19

Perfect!

    System.out.println("Enter a file name: ");
    String fileName = Keyboard.readInput();

    File myFile = new File(fileName);

    try (PrintWriter pw = new PrintWriter(new FileWriter(fileName))) {
        pw.write(??????);
    } catch (IOException e) {
        System.out.println(e.getMessage());
    }

Answer 1

已添加注释以澄清功能

package com.so.test;

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Scanner;

public class Main {

    //Declare StringBuilder as global.
    private static StringBuilder systemOut = new StringBuilder();

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        //Instead of writing only to System.out only also write to a StringBuilder
        writeLnToStreams("Hello!");
        //Attempt to write to File
        try {
            FileOutputStream outputStream = new FileOutputStream(scanner.nextLine());
            outputStream.write(systemOut.toString().getBytes());
        } catch (IOException e) {
            //Will write only to System.err
            e.printStackTrace();
        }
    }

    /**
     *
     * @param output the output to write to System.out and the global StringBuilder
     */
    private static void writeToStreams(String output) {
        System.out.println(output);
        systemOut.append(output);
    }

    /**
     *
     * @param output the output to write to System.out and the global StringBuilder
     */
    private static void writeLnToStreams(String output) {
        System.out.println(output);
        systemOut.append(output).append("\n");
    }
}

Answer 2

如果您希望创建一个允许您使用 System.out 的系统，以便在打印到控制台的同时打印到文件，您可以为 PrintStream 创建一个包装器以使其也可以写入到一个文件。可以这样做：

public void setupLogger() {
    PrintStream stream=System.out;
    try {
        File file=new File(System.getProperty("user.dir")+"/log.txt");
        file.delete();
        file.createNewFile();
        System.setOut(new WrapperPrintStream(stream,file));
    } catch (IOException e) {
        e.printStackTrace();
    }

    for (int i = 0; i <100 ; i++) {
        System.out.println("Log test "+i);
    }


}
class WrapperPrintStream extends PrintStream{

    private PrintStream defaultOutput;

    public WrapperPrintStream(@NotNull PrintStream out, File file) throws FileNotFoundException {
        super(new PrintStream(new FileOutputStream(file),true), true);
        defaultOutput =out;

    }

    @Override
    public void println(String x) {
        super.println(x);
        defaultOutput.println(x);
    }

    @Override
    public void println() {
        super.println();
        defaultOutput.println();
    }
    //etc for all methods.
}

但是，我建议使用像 Log4J 这样的 API，它会自动为您完成这一切。

Answer 3

起初我不太理解这个问题，但我想我现在明白了。我的演示使用输入和输出方法，类似于 GurpusMaximus 在他的回答中展示的（对他+1），但我使用不同的方法来获取输入和写入输出。

这是一个示例演示：

BufferedReader inputStream = null;
PrintWriter outputStream = null;
String writeString = "";

public void testMethod() {

    File file = new File("text.txt");

    try {
        inputStream = new BufferedReader(new InputStreamReader(System.in));
        outputStream = new PrintWriter(file);

        // Example console text
        println("Enter some text: ");
        String str = read();
        println("Entered: "+str);

        // Do this when you are done with the console and want to write to the file
        outputStream.print(writeString);
        inputStream.close();
        outputStream.close();

    } catch (IOException e) {
        e.printStackTrace();
    }
}

// Custom print method that also saves what was printed
public void println(String str) {
    System.out.println(str);
    writeString += str + System.lineSeparator(); // You can use the line separator call
                                                 // to format the text on different lines in
                                                 // the file, if you want that
}

// Custom read method that gets user input and also saves it
public String read() {
    try {
        String str = inputStream.readLine();
        writeString += str + System.lineSeparator();
        return str;
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

如果这与您正在寻找的内容更相关，请告诉我。

将已完成程序（在控制台上）的结果打印到文本文件？

Printing the results of a completed program (on the console) to a text file?

java

file-io

printwriter