Java IO不显示文件数据

Question

好吧，我想我被困在这里了。无法从文件中获取值以显示在JOptionPane的消息对话框中，该对话框包含在while循环中。现在我不知道输入/输出流的哪个方法用来显示这个文件上的所有数据，我认为被序列化为UTF8?

请告诉我做什么，什么东西我错过了，因为我是新的java。io类。

同样，文件StudentData。很少有人给我。并不是我不想自己做研究因为我已经做过了，我只是被困住了。我读了Javadoc，但是我现在一点头绪也没有。

import java.io.*;
import javax.swing.JOptionPane;
public class MyProj {

public void showMenu() {
    String choice = JOptionPane.showInputDialog
    (null, "Please enter a number: " + "n[1] All Students" + "n[2] BSCS Students" + "n[3] BSIT Students"
    + "n[4] BSA Students" + "n[5] First Year Students" + "n[6] Second Year Students" + "n[7] Third Year Students" 
    + "n[8] Passed Students" + "n[9] Failed Students" + "n[0] Exit");
    int choiceConvertedString = Integer.parseInt(choice);
    switch(choiceConvertedString){
        case 0:
            JOptionPane.showMessageDialog(null, "Program closed!");
            System.exit(1);
            break;
    }
}
DataInputStream myInputStream;
OutputStream myOutputStream;
int endOfFile = -1;
double grades;
int studentNo;
int counter;
String studentName;
String studentCourse;
public void readFile()
{
    try
    {
        myInputStream = new DataInputStream
            (new FileInputStream("C:\Users\Jordan's Pc\Documents\NetBeansProjects\MyProj\StudentData.feu"));
        try{
            while((counter=myInputStream.read()) != endOfFile)
            {
            studentName = myInputStream.readUTF();
            studentCourse = myInputStream.readUTF();
            grades = myInputStream.readDouble();
            JOptionPane.showMessageDialog
            (null, "StdNo: " + studentNo + "n"
                    + "Student Name: " + studentName + "n"
                    + "Student Course: " + studentCourse + "n"
                    + "Grades: " + grades);
            }
        }
        catch(FileNotFoundException fnf){
            JOptionPane.showMessageDialog(null, "File Not Found");
        }
    }/* end of try */
        catch(EOFException ex)
        {
            JOptionPane.showMessageDialog(null, "Processing Complete");
        }
        catch(Exception e)
        {
            JOptionPane.showMessageDialog(null, "An error occured");
        }
} 

}

Answer 1

while((counter=myInputStream.read()) != endOfFile)

问题可能在这里。你正在读取一个字节，然后把它扔掉。文件不太可能包含像这样的额外字节，这些字节是要被丢弃的。正确的循环应该是这样的:

try
{
    for (;;)
    {
        // .... readUTF() etc
    }
}
catch (EOFException exc)
{
    // You've read to end of file.
}
// catch IOException etc.