这是我的申请。我在保存对象并打开它们时遇到问题。当我尝试保存它时告诉我save.writeObject（firstName）中的变量无法解析为变量。
问题出在ActionPeformed块中：
import java.awt.*;
import java.awt.event.*;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import java.util.*;
public class ClassRoomFrameTest
{
public static void main(String[] args)
{
ClassRoomFrame frame = new ClassRoomFrame();
frame.setSize(600,600);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.setResizable(false);
frame.setLocationRelativeTo(null);
}
}
class ClassRoomFrame extends JFrame implements ActionListener
{
private JPanel mainPanel = new JPanel();
private JPanel deptPanel = new JPanel(new GridLayout(2,3));
private JPanel studentPanel = new JPanel(new GridLayout(2,5));
private JPanel displayPanel = new JPanel(new BorderLayout());
private JPanel buttonPanel = new JPanel(new GridLayout(1,2));
private JPanel menuBar = new JPanel();
private JTextArea textArea = new JTextArea();
private JScrollPane scrollPane = new JScrollPane(textArea);
private JLabel classLocationLabel = new JLabel("Class Location");
private JLabel classRoomLabel = new JLabel("Class Room Number");
private JLabel classCapacityLabel = new JLabel("Class Capacity");
private JTextField classLocationField = new JTextField();
private JTextField classRoomField = new JTextField();
private JTextField classCapacityField = new JTextField();
private JLabel studentFNameLabel = new JLabel("First name");
private JLabel studentLNameLabel = new JLabel("Last name");
private JLabel studentIDLabel = new JLabel("ID Number");
private JLabel studentMajorLabel = new JLabel("Major");
private JLabel studentCreditsLabel = new JLabel("Credits");
private JTextField studentFNameField = new JTextField();
private JTextField studentLNameField = new JTextField();
private JTextField studentIDField = new JTextField();
private JTextField studentMajorField = new JTextField();
private JTextField studentCreditsField = new JTextField();
private JButton addButton = new JButton("Add");
private JButton displayButton = new JButton("Display");
private JMenuBar menu = new JMenuBar();
private JMenu fileMenu = new JMenu("File");
private JMenuItem save = new JMenuItem("Open");
private JMenuItem open = new JMenuItem("Save");
private JFileChooser chooser = new JFileChooser();
Classroom room = null;
public ClassRoomFrame()
{
deptPanel.setPreferredSize(new Dimension(600,50));
deptPanel.setBorder(new EmptyBorder(new Insets(5,15,5,15)));
deptPanel.add(classLocationLabel);
deptPanel.add(classRoomLabel);
deptPanel.add(classCapacityLabel);
deptPanel.add(classLocationField);
deptPanel.add(classRoomField);
deptPanel.add(classCapacityField);
fileMenu.add(fileMenu);
fileMenu.add(open);
fileMenu.add(save);
menu.add(fileMenu);
studentPanel.setBorder(new EmptyBorder(new Insets(5,15,5,15)));
studentPanel.setPreferredSize(new Dimension(600,50));
studentPanel.setBorder(new EmptyBorder(new Insets(5,15,5,15)));
studentPanel.add(studentFNameLabel);
studentPanel.add(studentLNameLabel);
studentPanel.add(studentIDLabel);
studentPanel.add(studentMajorLabel);
studentPanel.add(studentCreditsLabel);
studentPanel.add(studentFNameField);
studentPanel.add(studentLNameField);
studentPanel.add(studentIDField);
studentPanel.add(studentMajorField);
studentPanel.add(studentCreditsField);
scrollPane.setBorder(new BevelBorder(BevelBorder.LOWERED));
scrollPane.setPreferredSize(new Dimension(600,450));
textArea.setBorder(new EmptyBorder(new Insets(5,15,5,15)));
buttonPanel.setBorder(new BevelBorder(BevelBorder.RAISED));
buttonPanel.setPreferredSize(new Dimension(600, 50));
buttonPanel.add(addButton);
buttonPanel.add(displayButton);
addButton.addActionListener(this);
addButton.setActionCommand("Add");
displayButton.addActionListener(this);
displayButton.setActionCommand("Display");
open.addActionListener(this);
open.setActionCommand("Open");
save.addActionListener(this);
save.setActionCommand("Save");
mainPanel.add(deptPanel);
mainPanel.add(studentPanel);
mainPanel.add(scrollPane);
add(menu, BorderLayout.NORTH);
add(mainPanel, BorderLayout.CENTER);
add(buttonPanel, BorderLayout.SOUTH);
}
@SuppressWarnings("unused")
public void actionPerformed(ActionEvent e)
{
/*---> HERE */if(e.getActionCommand().equals("Save"));
{
FileOutputStream saveFile = null;
ObjectOutputStream save = null;
try
{
saveFile = new FileOutputStream("ObjectData.txt");
save = new ObjectOutputStream(saveFile);
/*--->Error*/ save.writeObject(index);
save.writeObject(new Classroom());
} catch (FileNotFoundException e1)
{
e1.printStackTrace();
} catch (IOException e1)
{
e1.printStackTrace();
}
finally
{
try {saveFile.close();
}catch(Exception exc){
System.out.println(exc.getMessage());
}
}
}
/*---> Here*/if (e.getActionCommand().equals("Open"))
{
ObjectInputStream in = null;
int returnVal = chooser.showOpenDialog(ClassRoomFrame.this);
if (returnVal == JFileChooser.APPROVE_OPTION)
{
File file = chooser.getSelectedFile();
try {
in = new ObjectInputStream(new FileInputStream(file));
} catch (FileNotFoundException e1)
{
e1.printStackTrace();
} catch (IOException e1)
{
e1.printStackTrace();
}
}
try {
Student st = (Student)in.readObject();
Classroom cs = (Classroom)in.readObject();
System.out.println(st);
System.out.println(cs);
} catch (IOException e1) {
e1.printStackTrace();
} catch (ClassNotFoundException e1) {
e1.printStackTrace();
}
try{in.close();}
catch(Exception err){err.getMessage();}
}
if(e.getActionCommand().equals("Add"))
{
if(room == null)
{
room = new Classroom(classLocationField.getText(),
Integer.parseInt(classRoomField.getText()),
Integer.parseInt(classCapacityField.getText()));
room.addStudent(
new Student(studentFNameField.getText(),
studentLNameField.getText(),
studentIDField.getText(),
studentMajorField.getText(),
Integer.parseInt(studentCreditsField.getText())));
classLocationField.setEditable(false);
classRoomField.setEditable(false);
classCapacityField.setEditable(false);
studentFNameField.setText("");
studentLNameField.setText("");
studentIDField.setText("");
studentMajorField.setText("");
studentCreditsField.setText("");
textArea.setText("Class and first student added.");
}
else
{
room.addStudent(
new Student(studentFNameField.getText(),
studentLNameField.getText(),
studentIDField.getText(),
studentMajorField.getText(),
Integer.parseInt(studentCreditsField.getText())));
textArea.setText("Next student added.");
studentFNameField.setText("");
studentLNameField.setText("");
studentIDField.setText("");
studentMajorField.setText("");
studentCreditsField.setText("");
}
}
else if(e.getActionCommand().equals("Display"))
{
if (room != null)
{
textArea.setText(room.toString());
}
else
{
textArea.setText("Nothing to display");
}
}
}
}
class Student implements Serializable
{
public String firstName, lastName, studentIdNumber, studentMajor;
public int totalCourseCredits;
//-----------------------------------------------------------------
// Create an empty studentusing a default constructor.
//-----------------------------------------------------------------
public Student ()
{
}
//-----------------------------------------------------------------
// Creates a Student with the specified information.
//-----------------------------------------------------------------
public Student (String name1, String name2, String identification,
String myMajor, int myTotalCredits)
{
firstName = name1;
lastName = name2;
studentIdNumber = identification;
studentMajor = myMajor;
totalCourseCredits = myTotalCredits;
}
//-----------------------------------------------------------------
// Gets and sets first name.
//-----------------------------------------------------------------
public void setFirstName()
{
Scanner scan = new Scanner (System.in);
System.out.println ("Enter your First Name: ");
firstName = scan.nextLine();
}
//-----------------------------------------------------------------
// Gets and sets last name.
//-----------------------------------------------------------------
public void setLastName()
{
Scanner scan = new Scanner (System.in);
System.out.println ("Enter your Last Name: ");
lastName = scan.nextLine();
}
//-----------------------------------------------------------------
// Gets and sets Total Course Credits.
//-----------------------------------------------------------------
public void setTotalCredits()
{
Scanner scan = new Scanner (System.in);
System.out.println ("Enter your Total Credits: ");
totalCourseCredits = scan.nextInt();
}
//-----------------------------------------------------------------
// Gets and sets Student ID Number.
//-----------------------------------------------------------------
public void setIdNumber()
{
Scanner scan = new Scanner (System.in);
System.out.println ("Enter your ID Number: ");
studentIdNumber = scan.nextLine();
}
//-----------------------------------------------------------------
// Gets and sets Student Major.
//-----------------------------------------------------------------
public void setMajor()
{
Scanner scan = new Scanner (System.in);
System.out.println ("Enter your Major: ");
studentMajor = scan.nextLine();
}
public String toString()
{
String s = "First name: " + firstName + "\n" +
"Last name: " + lastName + "\n" +
"StudentID: " + studentIdNumber + "\n" +
"Student Major: " + studentMajor + "\n" +
"Course Creidts: " + totalCourseCredits + "\n";
return s;
}
}
class Classroom implements Serializable
{
private Student[] classRoster;
private int index = 0;
private int capacityStudents, roomNumber;
private String buildingLocation;
//-----------------------------------------------------------------
// Creates an empty Classroom.
//-----------------------------------------------------------------
public Classroom()
{
capacityStudents = 0;
roomNumber = 0;
buildingLocation = "";
}
//-----------------------------------------------------------------
// Creates a Classroom with the specified information.
//-----------------------------------------------------------------
public Classroom(String location, int room, int cap)
{
capacityStudents = cap;
roomNumber = room;
buildingLocation = location;
classRoster = new Student[capacityStudents];
}
//-----------------------------------------------------------------
// Gets and sets Building Location.
//-----------------------------------------------------------------
public void setBuilding()
{
Scanner scan = new Scanner (System.in);
System.out.println ("Enter the Building Location: ");
buildingLocation = scan.next();
}
//-----------------------------------------------------------------
// Gets and sets Room Number.
//-----------------------------------------------------------------
public void setRoomNumber()
{
Scanner scan = new Scanner (System.in);
System.out.println ("Enter the Room Number: ");
roomNumber = scan.nextInt();
}
//-----------------------------------------------------------------
// Sets Capacity of Students.
//-----------------------------------------------------------------
public void setCapacityStudents()
{
Scanner scan = new Scanner (System.in);
System.out.println ("Enter The Capacity of the Classroom: ");
capacityStudents = scan.nextInt();
classRoster = new Student[capacityStudents];
}
//-----------------------------------------------------------------
// Gets Capacity of Students.
//-----------------------------------------------------------------
public int getCapacityStudents()
{
return capacityStudents;
}
//-----------------------------------------------------------------
// Adds an Individual Student to the Classroom, checking if the
// capacity of the clasroom is full.
//-----------------------------------------------------------------
public void addStudent (Student student)
{
if(index < capacityStudents)
{
classRoster[index] = student;
index++;
}
else
{
System.out.println("Capacity exceeded! - Student cannot be added.");
}
}
//-----------------------------------------------------------------
// Adds an Individual Student to the Classroom, checking if the
// capacity of the clasroom is full.
//-----------------------------------------------------------------
public String toString()
{
StringBuffer sb = new StringBuffer
("Building: " + buildingLocation +
"\nClass room: " + roomNumber +
"\nCapacity: " + capacityStudents + "\n\n"
);
for(int i = 0; i < classRoster.length; i++)
{
if(classRoster[i] != null)
sb.append(classRoster[i].toString() + "\n");
}
return sb.toString();
}
}
答案 0 :(得分：1)
错误告诉您索引在save方法的范围内不可用。如果要保存索引，则需要在save方法中执行save.writeObject( classroom.getIndex())之类的操作。
答案 1 :(得分：1)
您已在index课程中声明ClassRoom变量。但是您尝试在actionPerformed类的方法ClassRoomFrame中使用它。
由于index的范围仅限于它的封闭类，因此如果不在ClassRoom类上使用实例，它将无法在其他类中显示。这就是编译器错误所说的：cannot find symbol