Question

我正在编写一个将数组对象写入java二进制文件的程序，然后将其读回。问题是当数组被回读时返回[null，null]。我没有正确地读/写对象吗？

DBMS.java

public static void writeToFile(Datab[] friends) {
    try {
        ObjectOutputStream myStream = new ObjectOutputStream(
                new FileOutputStream("datt.dat"));
        for(int i=0; i<friends.length; i++){
        myStream.writeObject(friends[i]);
        }
        myStream.close();
    }
     catch (FileNotFoundException e) {
    } catch (IOException e) {
    }

    System.out.println("\n\nArray written to file datt.");
}

/**********************************************************
 * readFromFile Read from the binary file and return the array of objects to
 * the calling method Catch the following exceptions: FileNotFoundException,
 * ClassNotFoundException, and the IOException (know what each does!)
 * 
 * @return The array as read in from the binary input file
 */
public static Datab[] readFromFile() {
    System.out
            .println("\n\nNow let's reopen the file and display the array.");
    Datab[] b = null;

    // The name of the file to open.
    String fileName = "datt.dat";

    try {
        // Use this for reading the data.
        byte[] buffer = new byte[1000];

        ObjectInputStream input = new ObjectInputStream(new FileInputStream("datt.dat"));

        input.close();

    } catch (FileNotFoundException ex) {
        System.out.println("Unable to open file '" + fileName + "'");
    } catch (IOException ex) {
        System.out.println("Error reading file '" + fileName + "'");
        // Or we could just do this:
        // ex.printStackTrace();
    }
    return b;

}

输出：在将数组写入输出文件之前的数组：

[Robert , Duchar 7345555555, Len , Gt 7345555567]

写入文件数据的数组。

现在让我们重新打开文件并显示数组。

从输入文件读入的数组... 你想要向后或向前看阵列吗？输入您的答案（b或f）：f

[null, null]

Answer 1

您正在使用null值初始化声明b。

Datab[] b = null;

然后您无法更新b

的值

最后，您将返回b，其初始化为null

对象无法正常读取

1 个答案: