这些错误消息是什么意思？ （Java秋千）

Question

我正在写一个GUI东西，它使某人可以自动将他们的学生分组。到目前为止，我已经到了输入学生并单击按钮进行设置的地步。但是，当我单击按钮时，会出现很多错误。

到目前为止，这是我拥有的代码：

import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Arrays;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTabbedPane;
import javax.swing.JTextPane;
import javax.swing.border.EmptyBorder;

public class StudentGrouper extends JFrame {

    private JPanel contentPane;

    private static ArrayList<String> students = new ArrayList<>();

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    StudentGrouper frame = new StudentGrouper();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public StudentGrouper() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 450, 300);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(new GridLayout(0, 1, 0, 0));

        JTabbedPane tabbedPane = new JTabbedPane(JTabbedPane.TOP);
        contentPane.add(tabbedPane);

        JScrollPane scrollPane = new JScrollPane();
        tabbedPane.addTab("Enter Students", null, scrollPane, null);

        JTextPane txtpnOneStudentPer = new JTextPane();
        txtpnOneStudentPer.setFont(new Font("Lucida Grande", Font.PLAIN, 14));
        txtpnOneStudentPer.setText("One student per line...");
        scrollPane.setViewportView(txtpnOneStudentPer);

        JButton btnSetStudentList = new JButton("Set Student List");
        btnSetStudentList.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e)
            {
                students = (ArrayList<String>) Arrays.asList(txtpnOneStudentPer.getText().split("\n"));
                System.out.println(students.get((int)(Math.random() * students.size())));
            }
        });
        btnSetStudentList.setFont(new Font("Lucida Grande", Font.PLAIN, 14));
        scrollPane.setColumnHeaderView(btnSetStudentList);

        JScrollPane scrollPane_1 = new JScrollPane();
        tabbedPane.addTab("Select Students", null, scrollPane_1, null);
    }

}

这是我收到的错误消息：

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.util.Arrays$ArrayList cannot be cast to java.util.ArrayList
    at StudentGrouper$2.actionPerformed(StudentGrouper.java:65)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
    at javax.swing.AbstractButton$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:6533)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
    at java.awt.Component.processEvent(Component.java:6298)
    at java.awt.Container.processEvent(Container.java:2236)
    at java.awt.Component.dispatchEventImpl(Component.java:4889)
    at java.awt.Container.dispatchEventImpl(Container.java:2294)
    at java.awt.Component.dispatchEvent(Component.java:4711)
    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:2746)
    at java.awt.Component.dispatchEvent(Component.java:4711)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
    at java.awt.EventQueue$4.run(EventQueue.java:731)
    at java.awt.EventQueue$4.run(EventQueue.java:729)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
    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)

谁能告诉我是什么原因导致这些错误发生？

（很明显，我想这些错误是由我匆忙跳过的一个小错误引起的。请告诉我！）

Answer 1

您正在使用students初始化ArrayList<String>，但是您的Arrays.asList不会创建“相同”的ArrayList类型。只需使用界面来确保您可以轻松地在列表类型之间切换：

private static List<String> students = new ArrayList<>();

这样，您可以删除演员表，并且可以正常使用

students = Arrays.asList(txtpnOneStudentPer.getText().split("\n"));