这个项目的目标是创建四个类:一个Student类、一个GradStudent类、一个Manager类和一个GUI类。在GUI中有两个单选按钮:一个用于Student，一个用于GradStudent。根据所选择的对象，Manager类应该负责使用两个数组创建和存储Student或GradStudent对象。我把所有的类都编出来了，但是当我选择其中一个单选按钮时，我在Manager中得到错误。getLastGradStudent，这反过来给了我一个错误在我的JRBListener类。我将在下面发布GUI和管理器类。任何帮助将非常感激!
经理类:
public class Manager {
private Student[] students = new Student[50];
private int counter1 = 0;
private GradStudent[] gradStudents = new GradStudent[50];
private int counter2 = 0;
public Manager() {
}
public void addStudent(String name, String address, String balance, String major) {
Student student1 = new Student(name, address, balance, major);
students[counter1] = student1;
counter1++;
}
public String getLastStudent() {
return "Student added: " + students[counter1-1] +"n";
}
public void addGradStudent(String name, String address, String balance, String major) {
GradStudent student2 = new GradStudent(name, address, balance, major);
gradStudents[counter2] = student2;
counter2++;
}
public String getLastGradStudent() {
return "Graduate Student added: " + gradStudents[counter2-1] +"n";
}
}
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.JRadioButton;
import javax.swing.ButtonGroup;
public class GUI extends JFrame {
private JRadioButton jrbStudent = new JRadioButton("Student");
private JRadioButton jrbGraduate = new JRadioButton("Graduate");
private JTextField name = new JTextField(20);
private JTextField address = new JTextField(20);
private JTextField balance = new JTextField(20);
private JTextField major = new JTextField(20);
private JButton jbtSubmit = new JButton("Submit");
private JTextArea echoStudent = new JTextArea();
private Manager m1 = new Manager();
public GUI() {
// Creates panel P1 and adds the components
JPanel p1 = new JPanel(new GridLayout(7, 1));
p1.add(new JLabel("Name: "));
p1.add(name);
p1.add(new JLabel("Address: "));
p1.add(address);
p1.add(new JLabel("Balance: "));
p1.add(balance);
p1.add(new JLabel("Major: "));
p1.add(major);
p1.add(jrbStudent);
p1.add(jrbGraduate);
p1.add(new JLabel("Submit Button: "));
p1.add(jbtSubmit);
p1.add(new JLabel("Submitted Text: "));
// Creates a radio-button group to group both buttons
ButtonGroup group = new ButtonGroup();
group.add(jrbStudent);
group.add(jrbGraduate);
// Adds the panel and text area to the frame
add(p1);
p1.add(echoStudent);
echoStudent.setEditable(false);
// Creates a listener and registers it with the submit button
SubmitListener l1 = new SubmitListener();
jbtSubmit.addActionListener(l1);
// Creates a listener and registers it with the radio buttons
JRBListener l2 = new JRBListener();
jrbStudent.addActionListener(l2);
jrbGraduate.addActionListener(l2);
}
// Class to handle the submit button
class SubmitListener implements ActionListener {
public void actionPerformed(ActionEvent a) {
Student[] students = new Student[50];
int arrayLocation = 0;
Student student1 = new Student(name.getText(), address.getText(),
balance.getText(), major.getText());
// Checks remaining array space
if (arrayLocation < 50) {
students[arrayLocation] = student1;
++arrayLocation;
}
// Echos back entered text while storing the previous text
echoStudent.setText(echoStudent.getText() + "n"
+ student1.toString());
}
}
// Class to handle the radio buttons
class JRBListener implements ActionListener {
public void actionPerformed(ActionEvent b) {
if(b.getSource() == jrbStudent)
m1.addStudent(name.getText(), address.getText(), balance.getText(), major.getText());
echoStudent.setText("Created Student: n" + m1.getLastStudent());
if(jrbGraduate.isSelected())
m1.addGradStudent(name.getText(), address.getText(), balance.getText(), major.getText());
echoStudent.setText("Created Graduate Student: n" + m1.getLastGradStudent());
}
}
public static void main(String[] args) {
GUI frame = new GUI();
frame.setTitle("Information Interface");
frame.setSize(1200, 900);
frame.setLocationRelativeTo(null); // Center the frame
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
我收到的错误:
Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: -1
at Manager.getLastGradStudent(Manager.java:28)
at GUI$JRBListener.actionPerformed(GUI.java:93)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.JToggleButton$ToggleButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
代码中的问题是，您没有设置任何括号来定义JRBListener.actionPerformed()方法中的if作用域。如果没有设置括号，则只有If -condition之后的下一行被认为在作用域中。因此，在您的情况下，无论是否添加了一个学生，程序将始终尝试声明"学生添加!"消息:-)这只有在您实际上添加了学生:
public void actionPerformed(ActionEvent b) {
if (b.getSource() == jrbStudent) {
m1.addStudent(name.getText(), address.getText(), balance.getText(), major.getText());
echoStudent.setText("Created Student: n" + m1.getLastStudent());
}
if (jrbGraduate.isSelected()) {
m1.addGradStudent(name.getText(), address.getText(), balance.getText(), major.getText());
echoStudent.setText("Created Graduate Student: n" + m1.getLastGradStudent());
}
}