问如何在java-netbeans中将文本框中的数据插入mysql数据库

EN

String sql="INSERT INTO ´donors´ (unit,name) VALUES (?,?)";
    //put the rest of the sentence
      try {
        PreparedStatement pdt = cn.prepareStatement(sql);
        pdt.setString(1, jTextField2.getText();
        pdt.setString(2, jTextField3.getText();
        //put the rest of the code
        int n1=pdt.executeUpdate();
      if(n1>0)
      {
      JOptionPane.showMessageDialog(null,"Inserted Successfully!");
      }
      }catch (SQLException ex) { }

private void btnSaveActionPerformed(java.awt.event.ActionEvent evt) {                                        
    String itemCode = txtItemCode.getText();
    String itemName = txtItemName.getText();
    String unitPrice = txtUnitPrice.getText();
    String qty = txtQty.getText();
    String query = "insert into items values ('"+itemCode+"','"+itemName+"','"+unitPrice+"','"+qty+"')";
    System.out.println(query);


    try {
        Connection c = DBClass.getConnection();
        Statement stmt = c.createStatement();
        stmt.executeUpdate(query);
        JOptionPane.showMessageDialog(this, "Saved");
    } catch (Exception e) {
        e.printStackTrace();
    }

import java.sql.Connection;
import java.sql.DriverManager;

/**
 *
 * @author Nadun
 */
public class DBClass {

    static private Connection  connection;

    public static Connection getConnection() throws Exception{
        if(connection == null){
            //JDBC
            Class.forName("com.mysql.jdbc.Driver");
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/stock", "root", "123");
        }
        return connection;
    }

}

try
{
 Class.forName("com.mysql.jdbc.Driver");
 conn=DriverManager.getConnection(DB_URL,USER,PASS);
 stmt = conn.createStatement();
 stmt.executeUpdate("insert into donors (name, age) values('"+d_name+"',,'"+Integer.valueOf(d_age.getText().toString())+"')");
 JOptionPane.showMessageDialog(null,"Inserted Successfully!");
 }
catch(Exception e){     }

}

Integer.valueOf(d_age.getText().toString());