GroupLayout Error: can't find wrong line
GroupLayout Error: can't find wrong line
package edu.uga.cs1302.gui;
import java.awt.event.*;
import java.io.*;
import java.text.ParseException;
import java.util.ArrayList;
import javax.swing.*;
public class StudentDirectory extends JFrame implements ActionListener{
private static final long serialVersionUID = 3294408483853747952L;
private Student current;
private ArrayList<Student> data;
private ArrayList<Student> unsavedData;
private ObjectOutputStream oos;
private FileOutputStream fos;
public StudentDirectory() throws FileNotFoundException{
JFrame frame = new JFrame("Student Directory");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.setSize(300,300);
data = new ArrayList<Student>();
unsavedData = new ArrayList<Student>();
current = new Student();
unsavedData.add(current);
try {
fos = new FileOutputStream("StudentsList.dat");
oos = new ObjectOutputStream(fos);
} catch (IOException e1) {
e1.printStackTrace();
}
JMenuBar mb = new JMenuBar();
JMenu file = new JMenu("File");
JMenuItem load = new JMenuItem("Load");
JMenuItem save = new JMenuItem("Save");
JMenuItem exit = new JMenuItem("Exit");
file.add(load);
file.add(save);
file.addSeparator();
file.add(exit);
mb.add(file);
frame.setJMenuBar(mb);
JPanel Pane = (JPanel) frame.getContentPane();
GroupLayout layout = new GroupLayout(Pane);
Pane.setLayout(layout);
layout.setAutoCreateGaps(true);
layout.setAutoCreateContainerGaps(true);
JLabel ID = new JLabel("ID:");
JTextField IDn = new JTextField();
IDn.setEditable(true);
JLabel first = new JLabel("First Name:");
JTextField firstN = new JTextField();
firstN.setEditable(true);
JLabel last = new JLabel("Last Name:");
JTextField lastN = new JTextField();
lastN.setEditable(true);
JLabel DOB = new JLabel("Date of Birth:");
JTextField dateN = new JTextField();
dateN.setEditable(true);
JLabel college = new JLabel("College:");
JTextField collegeN = new JTextField();
collegeN.setEditable(true);
JButton prev = new JButton("Previous");
JButton next = new JButton("Next");
JButton append = new JButton("Append");
prev.setEnabled(false);
layout.setHorizontalGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.TRAILING)
.addComponent(ID)
.addComponent(first)
.addComponent(last)
.addComponent(DOB)
.addComponent(college)
.addComponent(prev))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
.addComponent(IDn)
.addComponent(firstN)
.addComponent(lastN)
.addComponent(dateN)
.addComponent(collegeN)
.addGroup(layout.createSequentialGroup()
.addComponent(next)
.addComponent(append))
)
);
layout.setVerticalGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(ID)
.addComponent(IDn))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(first)
.addComponent(firstN))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(last)
.addComponent(lastN))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(DOB)
.addComponent(dateN))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(college)
.addComponent(collegeN))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(prev)
.addComponent(next)
.addComponent(append))
);
exit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
dispose();
System.exit(0);
}
}
);
load.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
try {
fos = new FileOutputStream("StudentsList.dat");
oos.reset();
for(int i = 0; i < data.size();i++){
oos.writeObject(data.get(i));
}
} catch (IOException e1) {
e1.printStackTrace();
}
}
});
save.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
try {
oos.flush();
oos.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
});
IDn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int index = unsavedData.indexOf(current);
unsavedData.remove(index);
String num = IDn.getText();
int idInput = Integer.parseInt(num);
current.setID(idInput);
unsavedData.add(index, current);
}
});
firstN.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int index = unsavedData.indexOf(current);
unsavedData.remove(index);
String currentFirst = firstN.getText();
current.setFirst(currentFirst);
unsavedData.add(index, current);
}
});
lastN.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int index = unsavedData.indexOf(current);
unsavedData.remove(index);
String currentLast = lastN.getText();
current.setLast(currentLast);
unsavedData.add(index, current);
}
});
dateN.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int index = unsavedData.indexOf(current);
unsavedData.remove(index);
String currentDOB = dateN.getText();
try {
current.setDOB(currentDOB);
} catch (ParseException e1) {
e1.printStackTrace();
}
unsavedData.add(index, current);
}
});
collegeN.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int index = unsavedData.indexOf(current);
unsavedData.remove(index);
String currentCollege = collegeN.getText();
current.setCollege(currentCollege);
unsavedData.add(index, current);
}
});
prev.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
int index = unsavedData.indexOf(current);
if(index!=0)
if(index-1==0){
prev.setEnabled(false);
}
current= unsavedData.get(index-1);
IDn.cut();
IDn.setText(""+current.getID());
firstN.cut();
firstN.setText(current.getFirst());
lastN.cut();
lastN.setText(current.getLast());
dateN.cut();
dateN.setText(current.getDOB());
collegeN.cut();
collegeN.setText(current.getCollege());
}
});
next.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
prev.setEnabled(true);
int index = unsavedData.indexOf(current);
if(index+1< unsavedData.size()){
current = unsavedData.get(index+1);
IDn.cut();
IDn.setText(""+current.getID());
firstN.cut();
firstN.setText(current.getFirst());
lastN.cut();
lastN.setText(current.getLast());
dateN.cut();
dateN.setText(current.getDOB());
collegeN.setText(current.getCollege());
}else{
current = new Student();
IDn.setText("");
firstN.setText("");
lastN.setText("");
dateN.setText("");
collegeN.setText("");
unsavedData.add(current);
}
index++;
}
});
append.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
data = new ArrayList<Student>();
for(int x = 0;x<unsavedData.size();x++){
data.add(unsavedData.get(x));
}
}
});
frame.pack();
frame.setVisible(true);
frame.validate();
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
}
}
主要方法
package edu.uga.cs1302.gui;
import java.io.FileNotFoundException;
import javax.swing.JFrame;
public class StudentMain {
public static void main(String[] args) throws FileNotFoundException{
new StudentDirectory();
}
}
当我使用 Prev 按钮时出现错误。
Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: javax.swing.JTextField[,0,0,0x0,invalid,layout=javax.swing.plaf.basic.BasicTextUI$UpdateHandler,alignmentX=0.0,alignmentY=0.0,border=com.apple.laf.AquaTextFieldBorder@154fd2c3,flags=288,maximumSize=,minimumSize=,preferredSize=,caretColor=javax.swing.plaf.ColorUIResource[r=0,g=0,b=0],disabledTextColor=javax.swing.plaf.ColorUIResource[r=128,g=128,b=128],editable=true,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],selectedTextColor=com.apple.laf.AquaImageFactory$SystemColorProxy[r=0,g=0,b=0],selectionColor=com.apple.laf.AquaImageFactory$SystemColorProxy[r=164,g=205,b=255],columns=0,columnWidth=0,command=,horizontalAlignment=LEADING] is not attached to a vertical group
at javax.swing.GroupLayout.checkComponents(GroupLayout.java:1090)
at javax.swing.GroupLayout.prepare(GroupLayout.java:1040)
at javax.swing.GroupLayout.layoutContainer(GroupLayout.java:910)
at java.awt.Container.layout(Container.java:1510)
at java.awt.Container.doLayout(Container.java:1499)
at java.awt.Container.validateTree(Container.java:1695)
at java.awt.Container.validateTree(Container.java:1704)
at java.awt.Container.validateTree(Container.java:1704)
at java.awt.Container.validate(Container.java:1630)
at javax.swing.RepaintManager.run(RepaintManager.java:711)
at javax.swing.RepaintManager.run(RepaintManager.java:709)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:708)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1731)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
at java.awt.EventQueue.access0(EventQueue.java:97)
at java.awt.EventQueue.run(EventQueue.java:709)
at java.awt.EventQueue.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.util.Calendar.setTime(Calendar.java:1770)
at java.text.SimpleDateFormat.format(SimpleDateFormat.java:943)
at java.text.SimpleDateFormat.format(SimpleDateFormat.java:936)
at java.text.DateFormat.format(DateFormat.java:345)
at edu.uga.cs1302.gui.Person.getDOB(Person.java:50)
at edu.uga.cs1302.gui.StudentDirectory.actionPerformed(StudentDirectory.java:234)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6535)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6300)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4891)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access0(EventQueue.java:97)
at java.awt.EventQueue.run(EventQueue.java:709)
at java.awt.EventQueue.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue.run(EventQueue.java:731)
at java.awt.EventQueue.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
我的学生 class 有几个参数（字符串名字、字符串姓氏、字符串日期、字符串学院、整数 ID）
在构造函数中将日期转换为简单日期格式 (MM-dd-yyyy) 的日期（可能是错误之一）
我的代码的要点：应该将 Students 的 ArrayList 加载到内存中。应该显示 ArrayList w GUI 的第一个 Student 的信息。信息导出到 "StudentsList.dat" 文件。单击 "Append" 按钮时保存到文件。
"File" 菜单包含三个菜单项："Load"、"Save"、"Exit"。
"Load" 将上述文件中的 Students ArrayList 加载到内存中。
"Save" 将 Students 的 ArrayList 保存到上面的文件中。
"Exit" 终止程序。
"Previous" 按钮返回到 ArrayList 中的前一个 Student。如果我们位于 ArrayList 的开头，则应禁用此按钮。
"Next" 按钮显示 ArrayList 中的后续 Student。如果我们位于 ArrayList 的末尾，则应禁用此按钮。
同样，我的建议是您根据 Swing 文档建议从 Swing 事件线程调用 GUI。例如：
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
// this is inside a "lambda" Runnable
try {
new StudentDirectory();
} catch (Exception e) {
e.printStackTrace();
}
});
}
package edu.uga.cs1302.gui;
import java.awt.event.*;
import java.io.*;
import java.text.ParseException;
import java.util.ArrayList;
import javax.swing.*;
public class StudentDirectory extends JFrame implements ActionListener{
private static final long serialVersionUID = 3294408483853747952L;
private Student current;
private ArrayList<Student> data;
private ArrayList<Student> unsavedData;
private ObjectOutputStream oos;
private FileOutputStream fos;
public StudentDirectory() throws FileNotFoundException{
JFrame frame = new JFrame("Student Directory");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.setSize(300,300);
data = new ArrayList<Student>();
unsavedData = new ArrayList<Student>();
current = new Student();
unsavedData.add(current);
try {
fos = new FileOutputStream("StudentsList.dat");
oos = new ObjectOutputStream(fos);
} catch (IOException e1) {
e1.printStackTrace();
}
JMenuBar mb = new JMenuBar();
JMenu file = new JMenu("File");
JMenuItem load = new JMenuItem("Load");
JMenuItem save = new JMenuItem("Save");
JMenuItem exit = new JMenuItem("Exit");
file.add(load);
file.add(save);
file.addSeparator();
file.add(exit);
mb.add(file);
frame.setJMenuBar(mb);
JPanel Pane = (JPanel) frame.getContentPane();
GroupLayout layout = new GroupLayout(Pane);
Pane.setLayout(layout);
layout.setAutoCreateGaps(true);
layout.setAutoCreateContainerGaps(true);
JLabel ID = new JLabel("ID:");
JTextField IDn = new JTextField();
IDn.setEditable(true);
JLabel first = new JLabel("First Name:");
JTextField firstN = new JTextField();
firstN.setEditable(true);
JLabel last = new JLabel("Last Name:");
JTextField lastN = new JTextField();
lastN.setEditable(true);
JLabel DOB = new JLabel("Date of Birth:");
JTextField dateN = new JTextField();
dateN.setEditable(true);
JLabel college = new JLabel("College:");
JTextField collegeN = new JTextField();
collegeN.setEditable(true);
JButton prev = new JButton("Previous");
JButton next = new JButton("Next");
JButton append = new JButton("Append");
prev.setEnabled(false);
layout.setHorizontalGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.TRAILING)
.addComponent(ID)
.addComponent(first)
.addComponent(last)
.addComponent(DOB)
.addComponent(college)
.addComponent(prev))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
.addComponent(IDn)
.addComponent(firstN)
.addComponent(lastN)
.addComponent(dateN)
.addComponent(collegeN)
.addGroup(layout.createSequentialGroup()
.addComponent(next)
.addComponent(append))
)
);
layout.setVerticalGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(ID)
.addComponent(IDn))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(first)
.addComponent(firstN))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(last)
.addComponent(lastN))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(DOB)
.addComponent(dateN))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(college)
.addComponent(collegeN))
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
.addComponent(prev)
.addComponent(next)
.addComponent(append))
);
exit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
dispose();
System.exit(0);
}
}
);
load.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
try {
fos = new FileOutputStream("StudentsList.dat");
oos.reset();
for(int i = 0; i < data.size();i++){
oos.writeObject(data.get(i));
}
} catch (IOException e1) {
e1.printStackTrace();
}
}
});
save.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
try {
oos.flush();
oos.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
});
IDn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int index = unsavedData.indexOf(current);
unsavedData.remove(index);
String num = IDn.getText();
int idInput = Integer.parseInt(num);
current.setID(idInput);
unsavedData.add(index, current);
}
});
firstN.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int index = unsavedData.indexOf(current);
unsavedData.remove(index);
String currentFirst = firstN.getText();
current.setFirst(currentFirst);
unsavedData.add(index, current);
}
});
lastN.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int index = unsavedData.indexOf(current);
unsavedData.remove(index);
String currentLast = lastN.getText();
current.setLast(currentLast);
unsavedData.add(index, current);
}
});
dateN.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int index = unsavedData.indexOf(current);
unsavedData.remove(index);
String currentDOB = dateN.getText();
try {
current.setDOB(currentDOB);
} catch (ParseException e1) {
e1.printStackTrace();
}
unsavedData.add(index, current);
}
});
collegeN.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int index = unsavedData.indexOf(current);
unsavedData.remove(index);
String currentCollege = collegeN.getText();
current.setCollege(currentCollege);
unsavedData.add(index, current);
}
});
prev.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
int index = unsavedData.indexOf(current);
if(index!=0)
if(index-1==0){
prev.setEnabled(false);
}
current= unsavedData.get(index-1);
IDn.cut();
IDn.setText(""+current.getID());
firstN.cut();
firstN.setText(current.getFirst());
lastN.cut();
lastN.setText(current.getLast());
dateN.cut();
dateN.setText(current.getDOB());
collegeN.cut();
collegeN.setText(current.getCollege());
}
});
next.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
prev.setEnabled(true);
int index = unsavedData.indexOf(current);
if(index+1< unsavedData.size()){
current = unsavedData.get(index+1);
IDn.cut();
IDn.setText(""+current.getID());
firstN.cut();
firstN.setText(current.getFirst());
lastN.cut();
lastN.setText(current.getLast());
dateN.cut();
dateN.setText(current.getDOB());
collegeN.setText(current.getCollege());
}else{
current = new Student();
IDn.setText("");
firstN.setText("");
lastN.setText("");
dateN.setText("");
collegeN.setText("");
unsavedData.add(current);
}
index++;
}
});
append.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
data = new ArrayList<Student>();
for(int x = 0;x<unsavedData.size();x++){
data.add(unsavedData.get(x));
}
}
});
frame.pack();
frame.setVisible(true);
frame.validate();
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
}
}
主要方法
package edu.uga.cs1302.gui;
import java.io.FileNotFoundException;
import javax.swing.JFrame;
public class StudentMain {
public static void main(String[] args) throws FileNotFoundException{
new StudentDirectory();
}
}
当我使用 Prev 按钮时出现错误。
Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: javax.swing.JTextField[,0,0,0x0,invalid,layout=javax.swing.plaf.basic.BasicTextUI$UpdateHandler,alignmentX=0.0,alignmentY=0.0,border=com.apple.laf.AquaTextFieldBorder@154fd2c3,flags=288,maximumSize=,minimumSize=,preferredSize=,caretColor=javax.swing.plaf.ColorUIResource[r=0,g=0,b=0],disabledTextColor=javax.swing.plaf.ColorUIResource[r=128,g=128,b=128],editable=true,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],selectedTextColor=com.apple.laf.AquaImageFactory$SystemColorProxy[r=0,g=0,b=0],selectionColor=com.apple.laf.AquaImageFactory$SystemColorProxy[r=164,g=205,b=255],columns=0,columnWidth=0,command=,horizontalAlignment=LEADING] is not attached to a vertical group
at javax.swing.GroupLayout.checkComponents(GroupLayout.java:1090)
at javax.swing.GroupLayout.prepare(GroupLayout.java:1040)
at javax.swing.GroupLayout.layoutContainer(GroupLayout.java:910)
at java.awt.Container.layout(Container.java:1510)
at java.awt.Container.doLayout(Container.java:1499)
at java.awt.Container.validateTree(Container.java:1695)
at java.awt.Container.validateTree(Container.java:1704)
at java.awt.Container.validateTree(Container.java:1704)
at java.awt.Container.validate(Container.java:1630)
at javax.swing.RepaintManager.run(RepaintManager.java:711)
at javax.swing.RepaintManager.run(RepaintManager.java:709)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:708)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1731)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
at java.awt.EventQueue.access0(EventQueue.java:97)
at java.awt.EventQueue.run(EventQueue.java:709)
at java.awt.EventQueue.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.util.Calendar.setTime(Calendar.java:1770)
at java.text.SimpleDateFormat.format(SimpleDateFormat.java:943)
at java.text.SimpleDateFormat.format(SimpleDateFormat.java:936)
at java.text.DateFormat.format(DateFormat.java:345)
at edu.uga.cs1302.gui.Person.getDOB(Person.java:50)
at edu.uga.cs1302.gui.StudentDirectory.actionPerformed(StudentDirectory.java:234)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6535)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6300)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4891)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access0(EventQueue.java:97)
at java.awt.EventQueue.run(EventQueue.java:709)
at java.awt.EventQueue.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue.run(EventQueue.java:731)
at java.awt.EventQueue.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
我的学生 class 有几个参数（字符串名字、字符串姓氏、字符串日期、字符串学院、整数 ID）
在构造函数中将日期转换为简单日期格式 (MM-dd-yyyy) 的日期（可能是错误之一）
我的代码的要点：应该将 Students 的 ArrayList 加载到内存中。应该显示 ArrayList w GUI 的第一个 Student 的信息。信息导出到 "StudentsList.dat" 文件。单击 "Append" 按钮时保存到文件。 "File" 菜单包含三个菜单项："Load"、"Save"、"Exit"。 "Load" 将上述文件中的 Students ArrayList 加载到内存中。 "Save" 将 Students 的 ArrayList 保存到上面的文件中。 "Exit" 终止程序。 "Previous" 按钮返回到 ArrayList 中的前一个 Student。如果我们位于 ArrayList 的开头，则应禁用此按钮。 "Next" 按钮显示 ArrayList 中的后续 Student。如果我们位于 ArrayList 的末尾，则应禁用此按钮。
同样，我的建议是您根据 Swing 文档建议从 Swing 事件线程调用 GUI。例如：
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
// this is inside a "lambda" Runnable
try {
new StudentDirectory();
} catch (Exception e) {
e.printStackTrace();
}
});
}