Question

有没有办法从命令行读取输入并将其写入文本文件？

public class Tester
{
    public static void main(String[] args)
        {
            //Yes, I am clueless so I have no idea what to put
        }
}

Answer 1

因为我假设你是Java的初学者，所以我写了一个带有不言自明的注释的简短代码示例。应用程序在命令行上运行并逐行读取，其中一行通过按Enter键结束。如果键入“EXIT”，应用程序将退出。要写入的文本文件位于C:\Folder\Text.txt。

这是一个非常基本的示例，因此只需将其扩展到您的需求即可。为了获得更好的平台独立性，您可以用\\替换硬编码的File.separator斜杠。作为finally块的注释：在较新版本的Java（＆gt; = 7）中，您可以使用try-with语法保存大量样板代码。如果您有兴趣，请阅读更多相关信息here。

您可以在教程here中了解基本的I / O机制。

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

public class Tester {

    public static void main(String[] args) {

        // The reader and writer objects must be declared BEFORE
        // the try block, otherwise they are not 'visible' to close
        // in the finally block
        Scanner reader = null;
        FileWriter writer = null;
        String inputText;

        try {

            // Reader and writer are instantiated within the try block,
            // because they can already throw an IOException
            reader = new Scanner(System.in);

            // Do not forget, '\\' is the escape sequence for a backslash
            writer = new FileWriter("C:\\Folder\\Text.txt");

            // We read line by line, a line ends with a newline character
            // (in Java a '\n') and then we write it into the file
            while (true) {

                inputText = reader.nextLine();

                // If you type 'EXIT', the application quits
                if (inputText.equals("EXIT")) {
                    break;
                }

                writer.write(inputText);

                // Add the newline character, because it is cut off by
                // the reader, when reading a whole line
                writer.write("\n");

            }

        } catch (IOException e) {

            // This exception may occur while reading or writing a line
            System.out.println("A fatal exception occurred!");

        } finally {

            // The finally branch is ALWAYS executed after the try
            // or potential catch block execution

            if (reader != null) {
                reader.close();
            }

            try {

                if (writer != null) {
                    writer.close();
                }

            } catch (IOException e) {

                // This second catch block is a clumsy notation we need in Java,
                // because the 'close()' call can itself throw an IOException.
                System.out.println("Closing was not successful.");

            }

        }

    }

}

Answer 2

使用Java 8，这可以非常简洁：

public static void main(String[] args) {
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    Stream<String> stream = in.lines().limit(20); // 20 is number of lines you want to read

    try (PrintWriter pw = new PrintWriter("FileName.txt", "UTF-8")) {
        stream.map(s -> s)
              .forEachOrdered(pw::println);
    }
     catch (UnsupportedEncodingException | FileNotFoundException e) {
        e.printStackTrace();
    }

Java - 读取键盘输入并将其写入文本文件

2 个答案: