Question

编写一个程序，要求用户输入整数（他们输入 -1完成数据输入）。这些数字将写入二进制文件文件。这将在名为writeBinaryFile()的方法中完成。然后程序应该读取二进制文件中的数字并显示他们到控制台。这应该在一个名为的方法中完成 readBinaryFile()。 main()方法应该只调用writeBinaryFile() 然后readBinaryFile()。

到目前为止我的代码：

public static void main(String[] args) throws FileNotFoundException, IOException {
    System.out.println("Please enter whole numbers then enter -1 to data entry.");
    writeBinaryFile();
    readBinaryFile();
}

/**
 * This method opens a binary file and writes the contents
 * of an int array to the file.
 */
private static void writeBinaryFile() throws IOException, FileNotFoundException
{
    Scanner input = new Scanner(System.in);
    ArrayList<Integer> number = new ArrayList<Integer>();
    try
    {
        FileOutputStream output = new FileOutputStream("Files//Numbers.dat");
        int numbers = 0;

        while(numbers != -1)
        {
            number.add(numbers = input.nextInt());

            output.write(numbers);
        }
        output.close();
    }
    catch(IOException ex)
    {
        ex.getMessage();
    }
}

private static void readBinaryFile() throws IOException
{
    FileInputStream input = new FileInputStream("Files//Numbers.dat");
    int value;
    value = input.read();
    System.out.print("The numbers in the file are:  ");
    try
    {
        while(value != -1)
        {
            System.out.print(value +" ");
            value = input.read();
        }
        input.close();
    }
    catch(IOException ex)
    {
        ex.getMessage();
    }
}

问题在于，当我输入此数据时：

5 2 4 6 8 4 -1

我的输出是：

5 2 4 6 8 4 255

如何阻止255出现？

Answer 1

您应该避免在输入中添加-1。问题在于：循环中number.add(numbers = input.nextInt());。

修改要编写二进制数据，您应该使用DataInputStream/DataOutputStream。您不能将其与Scanner混合，因为它主要用于文本数据。示例示例如下：

public static void main(String[] args) throws IOException { writeNumbers(); readNumbers(); } private static void writeNumbers() throws IOException { DataOutputStream output = new DataOutputStream(new FileOutputStream("C://Numbers.dat")); for (int i = 0; i < 10; i++) { output.writeInt(i); System.out.println(i); } output.close(); } private static void readNumbers() throws IOException{ DataInputStream input = new DataInputStream(new FileInputStream("C://Numbers.dat")); while (input.available() > 0) { int x = input.readInt(); System.out.println(x); } input.close(); }

Answer 2

尝试这样做......

 while(numbers = input.nextInt())!=-1)
        {
            number.add(numbers);

            output.write(numbers);
        }

Answer 3

只需更新@akhul_mittal答案，即可使用Scanner读取标准输入。

public static void main(String[] args) throws IOException {
    writeNumbers();
    readNumbers();
}

private static void writeNumbers() throws IOException {
    DataOutputStream output = new DataOutputStream(new FileOutputStream("C://Numbers.dat"));
    Scanner scanner = new Scanner(System.in);
    int n = scanner.nextInt();
    while (n != -1) {
        output.writeInt(n);
        n = scanner.nextInt();
    }
    output.close();
}

private static void readNumbers() throws IOException {
    DataInputStream input = new DataInputStream(new FileInputStream("C://Numbers.dat"));
    while (input.available() > 0) {
        int x = input.readInt();
        System.out.println(x);
    }
    input.close();
}

如何写和读取dat文件

3 个答案: