Java编程: Storing Objects and Arrays into a file

Question

*我的作业是编写一个程序，存储五个 int 值 1、2、3、4 和 5 的数组、当前时间的 Date 对象和 double 值 5.5。到名为 Exercies19_2.txt 的文件中。接下来，我将在程序中编写一个方法，打开Exercises19_2.txt，读取数据并显示到命令窗口。当我运行我的程序时，我不断收到以下消息:

Exception in thread "main" java.io.OptionalDataException at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.readObject(Unknown Source) at WriteArray.main(WriteArray.java:29).

你能帮我找出我做错了什么吗？？？这是我写的:

    import java.io.*;

    public class WriteArray {

    public static void main(String[] args)throws ClassNotFoundException,IOException {
    int[] numbers = {1, 2, 3, 4, 5};

    //Create an output stream for file
    ObjectOutputStream output = new ObjectOutputStream
    (new FileOutputStream("Exercises19_2.txt", true));

    //Write to file
      output.writeDouble(5.5);
      output.writeObject(numbers);
      output.writeObject(new java.util.Date());
      output.writeUTF("Exercises19_2.txt");

    //Close the stream
      output.close();

     //Create an input stream for file
     ObjectInputStream input = new ObjectInputStream
           (new FileInputStream("Exercises19_2.txt"));

     int[]newNumbers = (int[])(input.readObject());
       for (int i = 0; i < newNumbers.length; i++)
         System.out.println("Integers: " + newNumbers[i] + " ");

    String FileName= input.readUTF();
    double Double = input.readDouble();
    java.util.Date date = (java.util.Date)(input.readObject());
      System.out.println("DateTime: " + date);


    //Display the output

    System.out.println("Double: " + " " + input.readDouble());
    System.out.println("FileName: " + " " + input.readUTF());

    //Close the stream
     input.close();


      }
    }

Answer 1

当序列化和反序列化到 objectOutputStream 时，您必须按照写入对象的顺序读入对象。您写入文件的第一件事是带有 output.writeDouble(5.5); 的 double ，因此您需要先读回 double ，然后才能读取数字数组。