打开文件并存储消息。将消息读入字符串变量以打印。Java/Netbeans

嘿，我正在做的这个练习需要一些帮助。我必须打开一个名为hello.txt的文件，然后存储信息hello World！在文件中。然后我必须关闭文件并打开它，然后将消息读入字符串变量以打印它。到目前为止，我有以下代码。你对我如何成功编译这段代码有什么建议吗

package ProgrammingExercise11;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Scanner;

public class Input {

    public static void main(String[] args) throws FileNotFoundException
    {
        Scanner in = new Scanner(System.in);
        File inputFile = new File(hello.txt);
        Scanner in = new Scanner(inputFile);
        PrintWriter out = new PrintWriter(hello.txt);
        out.println("Hello, World!");
        String line = in.nextLine();
        in.close();
        out.close();
    }

}

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Java7之后的Files类提供了对文件、目录或其他类型的文件进行操作的静态方法，这更简单、更灵活

String file = "hello.txt";
Path filePath = Paths.get(file);
if (Files.isRegularFile(filePath)) {
    try(OutputStream fos = new FileOutputStream(file);
        InputStream fis = new FileInputStream(file)){
        // write message to file.
        String message = "Hello World!";
        byte[] messageBytes = message.getBytes();
        fos.write(messageBytes);

        // read message from file.
        byte[] receivedBytes = new byte[fis.available()];
        fis.read(receivedBytes);
        System.out.println(new String(receivedBytes));
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

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好的，让我们回答你的问题

Scanner in = new Scanner(System.in);
        File inputFile = new File(hello.txt);
        Scanner in = new Scanner(inputFile);
        PrintWriter out = new PrintWriter(hello.txt);
        out.println("Hello, World!");
        String line = in.nextLine();
        in.close();
        out.close();

您的代码无法编译，因为您在中引入了两个同名变量，并且没有声明hello.txt。 按照你的想法解决它

 public static void main(String[] args) throws Exception {
            String filePath = "hello.txt";
            File inputFile = new File(filePath);

            PrintWriter printWriter = new PrintWriter(inputFile);
            printWriter.write("Hello World!");
            printWriter.close();

            InputStream is = new FileInputStream(inputFile.getPath());
            BufferedReader buf = new BufferedReader(new InputStreamReader(is));
            String line = buf.readLine();
            System.out.println(line);

            is.close();
            buf.close();

    }

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