点击按钮后GUI冻结

我正在尝试创建客户端/服务器应用程序。问题是客户端上的确认按钮在第一次输入时工作，但如果我为另一个输入点击相同的按钮，则客户端GUI将冻结。点击按钮后GUI冻结

为什么GUI会冻结？

客户：

public class ClientGui 
{ 

private JFrame frmBookPointOf; 
private JTextField txtRm; 
private JTextArea txtrBookDetails; 
private JTextField textField; 
private JTextField textField_1; 
private JTextField textField_2; 
private JTextField textField_3; 
private JTextField textField_4; 
private JTextField textField_5; 
private JComboBox comboBox_1; 
private JComboBox comboBox; 
private dbController dbCtrl; 
private Connection conn; 
private static Socket client; 
private static BufferedReader fromServer = null; 
private static DataOutputStream toServer = null; 

/** 
* Launch the application. 
*/ 
public static void main(String[] args) { 

    try { 


     client = new Socket("127.0.0.1", 9090); 

     toServer = 
       new DataOutputStream(client.getOutputStream()); 
     fromServer = new BufferedReader(
        new InputStreamReader(client.getInputStream())); 

     String answer = fromServer.readLine(); 
     JOptionPane.showMessageDialog(null, "Connected!\n" + answer, "Status", JOptionPane.INFORMATION_MESSAGE);    

    } catch (UnknownHostException e) { 
     // TODO Auto-generated catch block 
     JOptionPane.showMessageDialog(null, e, "Error!", JOptionPane.ERROR_MESSAGE); 
     System.exit(0); 
    } catch (IOException e) { 
     // TODO Auto-generated catch block 
     JOptionPane.showMessageDialog(null, e, "Error!", JOptionPane.ERROR_MESSAGE); 
     System.exit(0); 
    } 

    EventQueue.invokeLater(new Runnable() 
    { 
     public void run() { 
      try { 
       ClientGui window = new ClientGui(); 
       window.frmBookPointOf.setVisible(true); 
      } catch (Exception e) { 
       e.printStackTrace(); 
      } 
     } 
    }); 
} 

/** 
* Create the application. 
*/ 
/** 
* 
*/ 
public ClientGui() 
{ 

    frmBookPointOf = new JFrame(); 
    frmBookPointOf.setTitle("Book Point of Sales"); 
    frmBookPointOf.setBounds(100, 100, 850, 500); 
    frmBookPointOf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

    JLabel lblIsbn = new JLabel("ISBN:"); 

    String[] index = {"--Select ISBN--"}; 
    comboBox = new JComboBox(index); 
    comboBox.setToolTipText(""); 

    dbCtrl = new dbController(); 
    try { 
     conn = dbCtrl.getConnection(); 
     String sql = "select isbn from book"; 
     PreparedStatement ps = conn.prepareStatement(sql); 
     ResultSet result = ps.executeQuery(); 

     while (result.next()) 
     { 
      comboBox.addItem(result.getString("isbn")); 

     } 
     conn.close(); 
    } catch (Exception e1) { 
     // TODO Auto-generated catch block 
     e1.printStackTrace(); 
    } 

    JLabel lblNewLabel = new JLabel("Price:"); 

    JLabel lblNewLabel_1 = new JLabel("Quantity:"); 

    JLabel lblNewLabel_2 = new JLabel("Discount:"); 

    txtRm = new JTextField(); 
    txtRm.setEditable(false); 
    txtRm.setColumns(10); 

    comboBox.addActionListener(new ActionListener() 
    { 
     public void actionPerformed(ActionEvent e) { 
      try { 
       conn = dbCtrl.getConnection(); 
       String x = comboBox.getSelectedItem().toString(); 
       String sql = "select price from book where isbn= '"+x+"'"; 
       PreparedStatement ps = conn.prepareStatement(sql); 
       ResultSet result = ps.executeQuery(); 

       StringBuilder strBuilder = new StringBuilder(); 
       while (result.next()) 
       { 
        strBuilder.append(result.getString(1)); 
       } 
       txtRm.setText(strBuilder.toString()); 
       conn.close(); 
      } catch (Exception e1) { 
       // TODO Auto-generated catch block 
       e1.printStackTrace(); 
      } 
     } 
    }); 


    textField = new JTextField(); 
    textField.setColumns(10); 

    comboBox_1 = new JComboBox(); 
    comboBox_1.addItem("0"); 
    comboBox_1.addItem("5"); 
    comboBox_1.addItem("10"); 
    comboBox_1.addItem("20"); 
    comboBox_1.addItem("30"); 


    JButton btnNewButton = new JButton("Clear"); 

    btnNewButton.addActionListener(new ActionListener() 
    { 
     public void actionPerformed(ActionEvent e) { 

      txtRm.setText(null); 
      txtrBookDetails.setText(null); 
      textField.setText(null); 
      comboBox.setSelectedIndex(0); 
      comboBox_1.setSelectedIndex(0); 
     } 

    }); 

    JButton btnNewButton_1 = new JButton("Confirm"); 

    btnNewButton_1.addActionListener(new ActionListener() 
    { 
     public void actionPerformed(ActionEvent e) 
     { 
      Confirm(); 
     } 
    }); 

    JLabel lblNewLabel_3 = new JLabel("Sub Total:"); 

    JLabel lblTotalItem = new JLabel("Total Item:"); 

    JLabel lblTotalPrice = new JLabel("Total Price:"); 

    JLabel lblP = new JLabel("Cash:"); 

    JLabel lblNewLabel_4 = new JLabel("Remainder:"); 

    textField_1 = new JTextField(); 
    textField_1.setEditable(false); 
    textField_1.setColumns(10); 

    textField_2 = new JTextField(); 
    textField_2.setEditable(false); 
    textField_2.setColumns(10); 

    textField_3 = new JTextField(); 
    textField_3.setEditable(false); 
    textField_3.setColumns(10); 

    textField_4 = new JTextField(); 
    textField_4.setColumns(10); 

    textField_5 = new JTextField(); 
    textField_5.setEditable(false); 
    textField_5.setColumns(10); 

    JButton btnNewButton_2 = new JButton("Cash"); 

    btnNewButton_2.addActionListener(new ActionListener() 
    { 
     public void actionPerformed(ActionEvent e) 
     { 
      Clear(); 
     } 
    }); 

    JButton btnPrintReceipt = new JButton("Print Receipt"); 

    JLabel lblBookDetails = new JLabel("Book Details"); 

    txtrBookDetails = new JTextArea(); 
    txtrBookDetails.setLineWrap(true); 
    txtrBookDetails.setWrapStyleWord(true); 
    txtrBookDetails.setEditable(false); 

    comboBox.addActionListener(new ActionListener() 
    { 
     public void actionPerformed(ActionEvent e) { 
      try { 
       conn = dbCtrl.getConnection(); 
       String y = comboBox.getSelectedItem().toString(); 
       String sql = "select book_title,author,numPages from book where isbn= '"+y+"'"; 
       PreparedStatement ps = conn.prepareStatement(sql); 
       ResultSet result = ps.executeQuery(); 

       StringBuilder strBuilder = new StringBuilder(); 
       while (result.next()) 
       { 
        strBuilder.append("Title: "); 
        strBuilder.append(result.getString(1)); 
        strBuilder.append("\nAuthor: "); 
        strBuilder.append(result.getString(2)); 
        strBuilder.append("\nNumber of Pages: "); 
        strBuilder.append(result.getString(3)); 
       } 
       txtrBookDetails.setText(strBuilder.toString()); 
       conn.close(); 
      } catch (Exception e1) { 
       // TODO Auto-generated catch block 
       e1.printStackTrace(); 
      } 
     } 
    }); 



    JLabel lblSalesDetails = new JLabel("Sales Details"); 

    JTextArea txtrSalesDetails = new JTextArea(); 
    txtrSalesDetails.setLineWrap(true); 
    txtrSalesDetails.setEditable(false); 
    txtrSalesDetails.setWrapStyleWord(true); 

    GroupLayout groupLayout = new GroupLayout(frmBookPointOf.getContentPane()); 
    groupLayout.setHorizontalGroup(
     groupLayout.createParallelGroup(Alignment.LEADING) 
      .addGroup(groupLayout.createSequentialGroup() 
       .addContainerGap() 
       .addGroup(groupLayout.createParallelGroup(Alignment.LEADING) 
        .addGroup(groupLayout.createSequentialGroup() 
         .addGap(121) 
         .addComponent(btnNewButton, GroupLayout.PREFERRED_SIZE, 77, GroupLayout.PREFERRED_SIZE) 
         .addPreferredGap(ComponentPlacement.UNRELATED) 
         .addComponent(btnNewButton_1, GroupLayout.PREFERRED_SIZE, 80, GroupLayout.PREFERRED_SIZE)) 
        .addGroup(groupLayout.createSequentialGroup() 
         .addGroup(groupLayout.createParallelGroup(Alignment.LEADING) 
          .addComponent(lblNewLabel_1) 
          .addComponent(lblNewLabel) 
          .addComponent(lblIsbn) 
          .addComponent(lblNewLabel_2)) 
         .addGap(69) 
         .addGroup(groupLayout.createParallelGroup(Alignment.LEADING, false) 
          .addComponent(txtRm) 
          .addComponent(comboBox, GroupLayout.PREFERRED_SIZE, 201, GroupLayout.PREFERRED_SIZE) 
          .addComponent(comboBox_1, 0, 200, Short.MAX_VALUE) 
          .addComponent(textField) 
          .addComponent(textField_1, GroupLayout.DEFAULT_SIZE, 201, Short.MAX_VALUE) 
          .addComponent(textField_2, GroupLayout.DEFAULT_SIZE, 201, Short.MAX_VALUE) 
          .addComponent(textField_3, GroupLayout.DEFAULT_SIZE, 201, Short.MAX_VALUE) 
          .addComponent(textField_4, GroupLayout.DEFAULT_SIZE, 201, Short.MAX_VALUE) 
          .addComponent(textField_5, GroupLayout.DEFAULT_SIZE, 201, Short.MAX_VALUE) 
          .addGroup(groupLayout.createSequentialGroup() 
           .addComponent(btnNewButton_2) 
           .addPreferredGap(ComponentPlacement.UNRELATED) 
           .addComponent(btnPrintReceipt)))) 
        .addComponent(lblNewLabel_3) 
        .addComponent(lblTotalItem) 
        .addComponent(lblTotalPrice) 
        .addComponent(lblP) 
        .addComponent(lblNewLabel_4)) 
       .addGap(43) 
       .addGroup(groupLayout.createParallelGroup(Alignment.LEADING, false) 
        .addGroup(groupLayout.createSequentialGroup() 
         .addGroup(groupLayout.createParallelGroup(Alignment.LEADING) 
          .addComponent(lblSalesDetails) 
          .addComponent(lblBookDetails)) 
         .addGap(251)) 
        .addComponent(txtrSalesDetails, GroupLayout.DEFAULT_SIZE, 412, Short.MAX_VALUE) 
        .addComponent(txtrBookDetails)) 
       .addContainerGap(33, Short.MAX_VALUE)) 
    ); 
    groupLayout.setVerticalGroup(
     groupLayout.createParallelGroup(Alignment.LEADING) 
      .addGroup(groupLayout.createSequentialGroup() 
       .addGap(23) 
       .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
        .addComponent(comboBox, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE) 
        .addComponent(lblIsbn) 
        .addComponent(lblBookDetails)) 
       .addGroup(groupLayout.createParallelGroup(Alignment.LEADING) 
        .addGroup(groupLayout.createSequentialGroup() 
         .addGap(18) 
         .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
          .addComponent(txtRm, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE) 
          .addComponent(lblNewLabel)) 
         .addGap(18) 
         .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
          .addComponent(textField, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE) 
          .addComponent(lblNewLabel_1)) 
         .addGap(18) 
         .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
          .addComponent(comboBox_1, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE) 
          .addComponent(lblNewLabel_2)) 
         .addPreferredGap(ComponentPlacement.UNRELATED) 
         .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
          .addComponent(btnNewButton_1) 
          .addComponent(btnNewButton))) 
        .addGroup(groupLayout.createSequentialGroup() 
         .addPreferredGap(ComponentPlacement.RELATED) 
         .addComponent(txtrBookDetails, GroupLayout.PREFERRED_SIZE, 142, GroupLayout.PREFERRED_SIZE))) 
       .addGap(18) 
       .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
        .addComponent(lblNewLabel_3) 
        .addComponent(textField_1, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE) 
        .addComponent(lblSalesDetails)) 
       .addPreferredGap(ComponentPlacement.UNRELATED) 
       .addGroup(groupLayout.createParallelGroup(Alignment.TRAILING, false) 
        .addComponent(txtrSalesDetails, Alignment.LEADING) 
        .addGroup(Alignment.LEADING, groupLayout.createSequentialGroup() 
         .addGap(7) 
         .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
          .addComponent(lblTotalItem) 
          .addComponent(textField_2, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)) 
         .addGap(18) 
         .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
          .addComponent(lblTotalPrice) 
          .addComponent(textField_3, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)) 
         .addGap(18) 
         .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
          .addComponent(lblP) 
          .addComponent(textField_4, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)) 
         .addGap(18) 
         .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
          .addComponent(lblNewLabel_4) 
          .addComponent(textField_5, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)) 
         .addPreferredGap(ComponentPlacement.UNRELATED) 
         .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
          .addComponent(btnNewButton_2) 
          .addComponent(btnPrintReceipt)))) 
       .addContainerGap(89, Short.MAX_VALUE)) 
    ); 
    frmBookPointOf.getContentPane().setLayout(groupLayout); 
} 

public void Confirm() 
{ 

float numb = 0f; 
int numb1 = 0; 
int numb2 = 0; 
int numb3 = 0; 
float numb4 = 0f; 
String numbSub = null; 
String numbIte = null; 
String numbTot = null; 

try 
{ 
    numb = Float.parseFloat(txtRm.getText()); 
    numb1 = Integer.parseInt(textField.getText()); 
    numb2 = Integer.parseInt(comboBox_1.getSelectedItem().toString()); 
    numb3 = Integer.parseInt(textField_2.getText()); 
    numb4 = Float.parseFloat(textField_3.getText()); 
} 
catch (NumberFormatException ex) 
{} 


try 
{ 
    toServer.writeFloat(numb); 
    toServer.writeInt(numb1); 
    toServer.writeInt(numb2); 
    toServer.writeInt(numb3); 
    toServer.writeFloat(numb4); 

}catch (IOException e1) 
{ 
// TODO Auto-generated catch block 
e1.printStackTrace(); 
} 

try 
{ 
    numbSub = fromServer.readLine(); 
    numbIte = fromServer.readLine(); 
    numbTot = fromServer.readLine(); 

} catch (IOException e1) 
{ 
    e1.printStackTrace(); 
} 

    textField_1.setText(numbSub); 
    textField_2.setText(numbIte); 
    textField_3.setText(numbTot); 


    txtRm.setText(null); 
    txtrBookDetails.setText(null); 
    textField.setText(null); 
    comboBox.setSelectedIndex(0); 
    comboBox_1.setSelectedIndex(0); 

} 

public void Clear() 
{ 

float numb5 = 0f; 
float numb6 = 0f; 
String numbRem = null; 

try 
{ 

    numb5 = Float.parseFloat(textField_3.getText()); 
    numb6 = Float.parseFloat(textField_4.getText()); 

}catch (NumberFormatException ex) 
{ 
    System.out.println(ex); 
} 

try 
{ 
    toServer.writeFloat(numb5); 
    toServer.writeFloat(numb6); 

} catch (IOException e1) { 
    // TODO Auto-generated catch block 
    e1.printStackTrace(); 
} 

try 
{ 
    numbRem = fromServer.readLine(); 

}catch (IOException ex) 
{ 
    ex.printStackTrace(); 
} 

textField_5.setText(numbRem); 
} 

}

服务器：

public class ServerGui{ 

private JFrame frmBookServer; 
private static ServerSocket listener; 
private static Socket socket; 
private dbController dbCtrl; 
private Connection conn; 

/** 
* Launch the application. 
*/ 
public static void main(String[] args) throws IOException 
{ 
    listener = new ServerSocket(9090);     

    EventQueue.invokeLater(new Runnable() 
    { 
     public void run() 
     { 
      try { 
       ServerGui window = new ServerGui(); 
       window.frmBookServer.setVisible(true); 
      } catch (Exception e) { 
       e.printStackTrace(); 
      } 
     } 
    }); 
} 
/** 
* Create the application. 
* 
*/ 
public ServerGui() 
{ 

    frmBookServer = new JFrame(); 
    frmBookServer.setTitle("Book Server"); 
    frmBookServer.setBounds(100, 100, 800, 600); 
    frmBookServer.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

    JButton btnNewButton = new JButton("Start Server"); 

    JButton btnNewButton_1 = new JButton("Stop Server"); 

    JButton btnNewButton_2 = new JButton("Display Sales"); 

    final JTextArea txtrDetailsOfRequest = new JTextArea(); 
    txtrDetailsOfRequest.setEditable(false); 
    txtrDetailsOfRequest.setWrapStyleWord(true); 
    GroupLayout groupLayout = new GroupLayout(frmBookServer.getContentPane()); 
    groupLayout.setHorizontalGroup(
     groupLayout.createParallelGroup(Alignment.LEADING) 
      .addGroup(groupLayout.createSequentialGroup() 
       .addContainerGap() 
       .addGroup(groupLayout.createParallelGroup(Alignment.LEADING) 
        .addGroup(groupLayout.createSequentialGroup() 
         .addGap(10) 
         .addComponent(txtrDetailsOfRequest, GroupLayout.PREFERRED_SIZE, 742, GroupLayout.PREFERRED_SIZE)) 
        .addGroup(groupLayout.createSequentialGroup() 
         .addComponent(btnNewButton) 
         .addGap(18) 
         .addComponent(btnNewButton_1) 
         .addGap(18) 
         .addComponent(btnNewButton_2))) 
       .addGap(22)) 
    ); 
    groupLayout.setVerticalGroup(
     groupLayout.createParallelGroup(Alignment.LEADING) 
      .addGroup(groupLayout.createSequentialGroup() 
       .addContainerGap() 
       .addGroup(groupLayout.createParallelGroup(Alignment.BASELINE) 
        .addComponent(btnNewButton) 
        .addComponent(btnNewButton_1) 
        .addComponent(btnNewButton_2)) 
       .addPreferredGap(ComponentPlacement.UNRELATED) 
       .addComponent(txtrDetailsOfRequest, GroupLayout.PREFERRED_SIZE, 497, GroupLayout.PREFERRED_SIZE) 
       .addContainerGap(20, Short.MAX_VALUE)) 
    ); 
    frmBookServer.getContentPane().setLayout(groupLayout); 

    btnNewButton.addActionListener(new ActionListener() 
    { 
     @Override 
     public void actionPerformed(ActionEvent e) 
     { 

      txtrDetailsOfRequest.setText("Starting Server...."); 
      Thread t = new Thread() { 
       @Override 
       public void run() 
       { 
        try 
        {   
         while(true) 
         { 

           socket = listener.accept(); 
           PrintWriter toClient = new PrintWriter(socket.getOutputStream(), true); 
           toClient.println(new Date().toString());    

           ServerCalc(); 

         } 

        }catch (IOException e1) 
        { 
        // TODO Auto-generated catch block 
        e1.printStackTrace(); 
        } 
        try 
        { 
         sleep(10); // milliseconds 
        }catch (InterruptedException ex) {} 
       } 
      }; 
      t.start(); 
     } 
    }); 

    btnNewButton_1.addActionListener(new ActionListener() 
    { 
     @Override 
     public void actionPerformed(ActionEvent e) 
     { 
      txtrDetailsOfRequest.setText("Closing Server...."); 
       try 
       { 
        listener.close(); 
       } catch (IOException e1) 
       { 
        // TODO Auto-generated catch block 
        e1.printStackTrace(); 
       }    

     } 
    }); 

    btnNewButton_2.addActionListener(new ActionListener() 
    { 
     @Override 
     public void actionPerformed(ActionEvent e) 
     { 
      dbCtrl = new dbController(); 
      try { 
       conn = dbCtrl.getConnection(); 
       String sql = "select book_title,quantity from sales"; 
       PreparedStatement ps = conn.prepareStatement(sql); 
       ResultSet result = ps.executeQuery(); 

       StringBuilder strBuilder = new StringBuilder(); 
       while (result.next()) 
       { 
        strBuilder.append(result.getString(1)).append(" = ").append(result.getString(2)); 
        strBuilder.append("\n"); 

       } 
       txtrDetailsOfRequest.setText(strBuilder.toString()); 
       conn.close(); 

      } catch (Exception e1) { 
       // TODO Auto-generated catch block 
       e1.printStackTrace(); 
      } 

     } 
    }); 
} 
public void ServerCalc() 
{ 
    try{ 
      PrintWriter toClient = new PrintWriter(socket.getOutputStream(), true); 

      DataInputStream fromClient = new DataInputStream(socket.getInputStream()); 

      //calculate sub total, total item, total price 
      float numb = fromClient.readFloat(); 
      int numb1 = fromClient.readInt(); 
      int numb2 = fromClient.readInt(); 
      int numb3 = fromClient.readInt(); 
      float numb4 = fromClient.readFloat(); 


      float dis = (float) (numb2 * 0.01); 
      float numbSub =numb - ((dis) * numb); 
      float numbTot =(numbSub * numb1) + numb4; 
      int numbIte = numb1 + numb3; 


      toClient.println(numbSub); 
      toClient.println(numbIte); 
      toClient.println(numbTot); 

      //calculate cash remainder 
      float numb5 = fromClient.readFloat(); 
      float numb6 = fromClient.readFloat(); 

      float numbRem = numb6 - numb5; 

      toClient.println(numbRem); 
    }catch (IOException e1) { 
     // TODO Auto-generated catch block 
     e1.printStackTrace(); 
    } 

} 
}

来源

2013-03-25 user1907971

你应该看看其他问题。例如：http://stackoverflow.com/questions/13609644/java-swing-gui-window-hangs或http://stackoverflow.com/questions/4413310/setvisible-method-in-java-swing-hangs-system。我希望你会找到答案。 – 2013-03-25 13:57:22

当你点击一个按钮，触发的事件指派线程的ActionListener的actionPerformed方法。此线程是负责UI的一个且唯一的线程。

在您离开actionPerformed方法（线程被占用）之前，UI将保持冻结状态。因此，如果您的ActionListener块（例如您的fromServer.readLine()调用）阻止，该UI将保持冻结状态，直到该阻止呼叫结束。

这就是为什么通用指南是将长期任务卸载到工作线程的原因。 Swing concurrency tutorial包含更多信息。

来源

2013-03-25 14:04:35 Robin

+1，用于并发链接。 – camickr 2013-03-25 14:59:15

点击按钮后GUI冻结

回答

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