將由getInt（int）返回的值合併爲字符串是不允許的

getInt(int)是ResultSet的函數。在下面的代碼中，我無法理解爲什麼getInt(int)返回的integer不是String。其實我完全不確定發生了什麼問題。運行程序後，當我在文本字段中輸入一個整數並點擊「顯示員工」按鈕時，它會在應該發生裝箱的行中顯示一些錯誤（在case: "Show emplyee"的塊內）。所以經過檢查後，我覺得這是問題（雖然我不確定）。將由getInt（int）返回的值合併爲字符串是不允許的

下面的程序不完整。它應該建立一個GUI，它有6個按鈕來檢索和編輯數據庫（數據庫4）和文本字段中的數據以輸入輸入並顯示輸出。我是Java Swing的新手。如果有人能糾正我，會有很大的幫助。

import java.awt.*; 
import javax.swing.*; 
import java.awt.event.*; 
import java.sql.*; 
import java.util.logging.Level; 
import java.util.logging.Logger; 

public class GUI_emp implements ActionListener { 

JFrame f; 
JTextField tf; 

GUI_emp() { 
    f = new JFrame(); 
    f.setSize(300, 600); 
    f.setVisible(true); 
    tf = new JTextField("Enter id of Employee here"); 
    f.add(tf); 
    JButton b1 = new JButton("Add Employee"); 
    JButton b2 = new JButton("Edit Employee"); 
    JButton b3 = new JButton("Delete Employee"); 
    JButton b4 = new JButton("Show Employee"); 
    JButton bup = new JButton("Up"); 
    JButton bdo = new JButton("Down"); 

    b1.addActionListener(this); 
    b2.addActionListener(this); 
    b3.addActionListener(this); 
    b4.addActionListener(this); 
    bup.addActionListener(this); 
    bdo.addActionListener(this); 
    f.add(b1); 
    f.add(b2); 
    f.add(b3); 
    f.add(b4); 
    f.add(bup); 
    f.add(bdo); 

    f.setLayout(new GridLayout(7, 1)); 

} 

public static void main(String[] args) throws Exception { 
    new GUI_emp(); 
} 

public void datab4(JButton b) throws Exception { 

    //Class.forName("org.apache.derby.jdbc.ClientDriver"); 
    Connection con = DriverManager.getConnection("jdbc:derby://localhost:1527/datab4", "soc", "soc"); 
    PreparedStatement ps; 

    String ch = b.getText(); 
    switch (ch) { 

     case "Add Employee": { 
      int i = Integer.valueOf(tf.getText()); 
      ps = con.prepareStatement("insert into datab4 values(?,?,?,?)"); 
      ps.setInt(1, i); 
      String name = JOptionPane.showInputDialog("Enter name of employee"); 
      String salary = JOptionPane.showInputDialog("Enter salary of employee"); 
      String desig = JOptionPane.showInputDialog("Enter designation of employee"); 
      ps.setString(2, name); 
      ps.setInt(3, Integer.valueOf(salary)); 
      ps.setString(4, desig); 
      ps.execute(); 
      ps.close(); 
      break; 
     } 
     case "Edit Employee": { 
      int i = Integer.valueOf(tf.getText()); 
      ps = con.prepareStatement("update datab4 set Name=?, Salary=?, Designation=? where ID = ?"); 
      String name = JOptionPane.showInputDialog("Enter name of employee"); 
      String salary = JOptionPane.showInputDialog("Enter salary of employee"); 
      String desig = JOptionPane.showInputDialog("Enter designation of employee"); 
      ps.setInt(1, i); 
      ps.setString(2, name); 
      ps.setInt(3, Integer.valueOf(salary)); 
      ps.setString(4, desig); 
      ps.executeUpdate(); 
      ps.close(); 
      break; 
     } 
     case "Delete Employee": { 
      int i = Integer.valueOf(tf.getText()); 
      ps= con.prepareStatement("delete from datab4 where ID = ?"); 
      ps.setInt(1, i); 
      ps.executeUpdate(); 
      ps.close(); 
      break; 

     } 
     case "Show Employee": { 
      int i = Integer.valueOf(tf.getText()); 
      ps = con.prepareStatement("select * from datab4 where ID = ?"); 
      ps.setInt(1, i); 
      ResultSet rs = ps.executeQuery(); 
      tf.setText(String.valueOf(rs.getInt(1))+". "+"Name: "+rs.getString(2)+" Salary: "+String.valueOf(rs.getInt(3))+" Designation: "+rs.getString(4));//ERROR 
      break; 
     } 



    } 
} 

public void actionPerformed(ActionEvent e) { 
    JButton jb = (JButton) (e.getSource()); 
    try { 
     datab4(jb); 
    } catch (Exception ex) { 
     Logger.getLogger(GUI_emp.class.getName()).log(Level.SEVERE, null, ex); 
     } 
    } 
}

以下是錯誤：

PM gui_emp.GUI_emp actionPerformed 
SEVERE: null 
java.sql.SQLException: Invalid operation at current cursor position. 
    at org.apache.derby.client.am.SQLExceptionFactory.getSQLException(Unknown Source) 
    at org.apache.derby.client.am.SqlException.getSQLException(Unknown Source) 
    at org.apache.derby.client.am.ClientResultSet.getInt(Unknown Source) 
    at gui_emp.GUI_emp.datab4(GUI_emp.java:105) 
    at gui_emp.GUI_emp.actionPerformed(GUI_emp.java:117) 
    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) 
Caused by: ERROR XJ121: Invalid operation at current cursor position. 
    at org.apache.derby.client.am.ClientResultSet.checkForValidCursorPosition(Unknown Source) 
    at org.apache.derby.client.am.ClientResultSet.checkGetterPreconditions(Unknown Source) 
    ... 39 more

來源

2017-07-16 Shubham

'盒裝入String' - 有沒有這樣的事情 – Eran

@Eran我的意思'int'轉化爲' String'。 – Shubham

@LorisSecuro謝謝你找到我的重複。它回答了我的問題。 – Shubham

使用此

ResultSet rs = ps.executeQuery(); 
while(rs.next()){ 
    tf.setText(String.valueOf(rs.getInt(1))+". "+"Name: "+rs.getString(2)+" Salary: "+String.valueOf(rs.getInt(3))+" Designation: "+rs.getString(4)); 
}

來源

2017-07-16 11:49:38

通常，解釋代碼在回答問題時的功能。 –

將由getInt（int）返回的值合併爲字符串是不允許的

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