发生了一件奇怪的事。由于某种原因，它需要很长时间（1.60900秒），直到它运行以下行：
textArea = new JTextArea();
我将textArea变量声明为全局变量。 这只发生在一个窗口（Jframe）中。在其他情况下，它不会发生。
public class FAQ extends JFrame
{
/*--------attributes--------*/
private static final long serialVersionUID = 1L;
private JPanel contentPane;
private JPanel panel;
private JScrollPane scrollPaneInput;
private JScrollPane scrollPaneQuestions;
private JPanel paneQuestions;
private JPanel paneSelectOrNewFAQ;
private JButton btnEditSelection;
private JButton btnNewFAQ;
public JTextArea textArea;
private JLabel lblQuestions;
public JList list;
private User user;
private FAQ currentWindow;
private int selectedFaq = 0;
private DatabaseManager DManager;
private Vector<FAQ_class> Faqs = new Vector<FAQ_class>();
private JButton btnNewButton;
/*--------methods--------*/
public FAQ(User _user,DatabaseManager DM)
{
setResizable(false);
DManager = DM;
addWindowStateListener(new WindowStateListener() {
public void windowStateChanged(WindowEvent arg0) {
}
});
addWindowListener(new WindowAdapter() {
@Override
public void windowClosed(WindowEvent arg0) {
Menu menu = new Menu(user,DManager);
menu.setVisible(true);
}
});
currentWindow = this;
user = _user;
addGui();
if(!user.rule.equals("patient"))
{
btnEditSelection.setEnabled(true);
btnNewFAQ.setEnabled(true);
}
loadFaqs();
}//end of FAQ
public void loadFaqs()
{
Faqs = DManager.getQuestionsList();
Vector<String> temp = new Vector<String>();
for(int i = 0 ; i < Faqs.size();i++)
{
temp.addElement(Faqs.get(i).question);
}
list.setListData(temp);
}
public void addGui()
{
setTitle("FAQ - Online medical help");
setIconImage(Toolkit.getDefaultToolkit().getImage(FAQ.class.getResource("/Images/question.png")));
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
setBounds(100, 100, 708, 438);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(new GridLayout(1, 0, 0, 0));
addPanel();
addPanes();
addButtons();
addGroupLayout();
addJTextArea();
}//end of addGui
public void addPanel()
{
panel = new JPanel();
panel.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.add(panel);
}//end of addPanel
public void addPanes()
{
scrollPaneInput = new JScrollPane();
scrollPaneInput.setBounds(327, 0, 365, 398);
paneQuestions = new JPanel();
paneQuestions.setBounds(0, 0, 317, 38);
paneQuestions.setBackground(new Color(154, 205, 50));
}//end of addScrollPanes
public void addButtons()
{
}//end of addButtons
public void addJTextArea()
{
textArea = new JTextArea();
textArea.setEditable(false);
textArea.setFont(new Font("Courier New", Font.PLAIN, 14));
textArea.setLineWrap(true);
textArea.setWrapStyleWord(true);
textArea.setAlignmentX(Component.RIGHT_ALIGNMENT);
scrollPaneInput.setViewportView(textArea);
}//end of addJTextArea
public void addGroupLayout()
{
lblQuestions = new JLabel("Questions");
lblQuestions.setHorizontalAlignment(SwingConstants.CENTER);
lblQuestions.setBounds(0, 0, 317, 38);
lblQuestions.setForeground(new Color(255, 255, 255));
lblQuestions.setFont(new Font("Tahoma", Font.BOLD, 22));
panel.setLayout(null);
scrollPaneQuestions = new JScrollPane();
scrollPaneQuestions.setBounds(0, 37, 317, 318);
list = new JList();
list.setSelectionBackground(new Color(154, 205, 50));
list.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent arg0) {
try
{
for(int i = 0; i<Faqs.size();i++)
{
if(!list.isSelectionEmpty())
if(Faqs.get(i).question.equals(list.getSelectedValue().toString()))
{
textArea.setText(Faqs.get(i).answer);
selectedFaq = i;
break;
}
}
}
catch(Exception e)
{
e.printStackTrace();
}
}
});
scrollPaneQuestions.setViewportView(list);
panel.add(scrollPaneQuestions);
panel.add(paneQuestions);
paneQuestions.setLayout(null);
paneQuestions.add(lblQuestions);
panel.add(scrollPaneInput);
paneSelectOrNewFAQ = new JPanel();
paneSelectOrNewFAQ.setBounds(0, 348, 317, 50);
btnEditSelection = new JButton("Edit Selected");
btnEditSelection.setBounds(68, 11, 131, 40);
btnEditSelection.setEnabled(false);
btnEditSelection.addActionListener(new ActionListener() {
//open EditFAQ to edit FAQ
public void actionPerformed(ActionEvent e) {
if(!list.isSelectionEmpty())
{
EditFAQ faq = new EditFAQ(user,Faqs.get(selectedFaq),currentWindow,DManager);
faq.setVisible(true);
currentWindow.setEnabled(false);
}
else
{
JOptionPane.showMessageDialog(null,"You must select for the list first.");
}
}
});
btnEditSelection.setIcon(new ImageIcon(FAQ.class.getResource("/Images/tool.png")));
btnNewFAQ = new JButton("New FAQ");
btnNewFAQ.setBounds(203, 11, 114, 40);
btnNewFAQ.setEnabled(false);
btnNewFAQ.addActionListener(new ActionListener() {
//open EditFAQ to make new FAQ
public void actionPerformed(ActionEvent e) {
EditFAQ faq = new EditFAQ(user,null,currentWindow,DManager);
faq.setVisible(true);
currentWindow.setEnabled(false);
}
});
btnNewFAQ.setMinimumSize(new Dimension(95, 23));
btnNewFAQ.setMaximumSize(new Dimension(95, 23));
btnNewFAQ.setPreferredSize(new Dimension(95, 23));
btnNewFAQ.setIcon(new ImageIcon(FAQ.class.getResource("/Images/add.png")));
btnNewButton = new JButton("");
btnNewButton.setBounds(0, 10, 42, 41);
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
dispose();
}
});
btnNewButton.setIcon(new ImageIcon(FAQ.class.getResource("/Images/left.png")));
panel.add(paneSelectOrNewFAQ);
paneSelectOrNewFAQ.setLayout(null);
paneSelectOrNewFAQ.add(btnNewButton);
paneSelectOrNewFAQ.add(btnEditSelection);
paneSelectOrNewFAQ.add(btnNewFAQ);
}//end of addGroupLayout
}//end of class
答案 0 :(得分：1)
发生了一件奇怪的事。由于某种原因，它需要很长时间（5秒〜），直到它运行以下行：
运行此类并给我结果：
import java.text.DecimalFormat;
import java.text.NumberFormat;
import javax.swing.JTextArea;
public class JTextAreaRunningTime {
JTextArea textArea;
public JTextAreaRunningTime(){
long startTime = System.currentTimeMillis();
textArea = new JTextArea();
long endTime = System.currentTimeMillis();
NumberFormat nf = new DecimalFormat("#0.00000");
String totalTime = nf.format((endTime-startTime)/1000d);
System.out.println("Execution time is " + totalTime + " seconds");
}
public static void main (String...argW){
new JTextAreaRunningTime();
}
}