学生选课 java，却不能显示出来，帮我查查程序

[lllsssnnn]

class Course extends JFrame implements ActionListener {
Connection con = null;
Statement stmt = null;
ResultSet rs = null;
JLabel lb, label, lb2;
JButton btn1, btn3;
JTextArea ta;
JTextField tf;

Course() {

ImageIcon icon = new ImageIcon("D:/workspace-eclipse3.6/BYSJ/src/Images/OK.jpg "); /* 更改左上角图标 */
Image image = icon.getImage();
this.setIconImage(image);
label = new JLabel();

ImageIcon img=new ImageIcon("D:/workspace-eclipse3.6/BYSJ/src/Images/小模块.jpg");
label.setIcon(img);
add(label);

label.setLayout(new FlowLayout());

lb2 = new JLabel("欢迎来到课程信息查询界面", JLabel.CENTER);
lb2.setFont(new Font("Dialog", 1, 25));
lb2.setForeground(Color.red);

lb = new JLabel("请输入要查询课程名称：");
btn1 = new JButton("按课程名称查询");

btn3 = new JButton("关闭");
ta = new JTextArea(15, 30);
ta.setFont(new Font("楷体", Font.BOLD, 15));
tf = new JTextField(10);

label.add(lb2);
label.add(lb);
label.add(tf);
label.add(btn1);
label.add(ta);
label.add(btn3);
add(label);

setTitle("按课程名称查询");
setBounds(600, 210, 400, 500);
setVisible(true);
btn1.addActionListener(this);
btn3.addActionListener(this);

}

public void actionPerformed(ActionEvent e) {
boolean t = false;
ta.setText("");
if (e.getSource() == btn1) {
String str = tf.getText();

try {
String sql ="select * from dbo.course where cname like"+ "'" + str + "'";
con = BaseDao.openConnection();
stmt = con.createStatement();
rs = stmt.executeQuery(sql);
while (rs.next()) {
String cno = rs.getString("cno");
String cname = rs.getString("cname");
String cteacher = rs.getString("cteacher");
String cplace = rs.getString("cplace");
String clei = rs.getString("clei");

ta.append("课程编码:" + StringUtil.filterNull(cno) + "\n");
ta.append("课程名称:" + StringUtil.filterNull(cname) + "\n");
ta.append("授课教师:" + StringUtil.filterNull(cteacher) + "\n");
ta.append("上课地点:" + StringUtil.filterNull(cplace) + "\n");
ta.append("课程类型:" + StringUtil.filterNull(clei) + "\n");

t = true;

}
if (t == false)
JOptionPane.showMessageDialog(this, "无此课程！", "警告对话框",
JOptionPane.WARNING_MESSAGE);
con.close();
} catch (SQLException ex) {
ex.printStackTrace();
} finally {
BaseDao.closeAll(con, stmt, rs);

}

} else if (e.getSource() == btn3) {
dispose();
}
}
}

[-江沐风-]

有错误信息没？

[lllsssnnn]

com.microsoft.sqlserver.jdbc.SQLServerException: 没有为参数号 1 设置值。 at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:190) at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.buildParamTypeDefinitions(SQLServerPreparedStatement.java:260) at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.buildPreparedStrings(SQLServerPreparedStatement.java:219) at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.doPrepExec(SQLServerPreparedStatement.java:612) at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.doExecutePreparedStatement(SQLServerPreparedStatement.java:400) at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement$PrepStmtExecCmd.doExecute(SQLServerPreparedStatement.java:350) at com.microsoft.sqlserver.jdbc.TDSCommand.execute(IOBuffer.java:5696) at com.microsoft.sqlserver.jdbc.SQLServerConnection.executeCommand(SQLServerConnection.java:1715) at com.microsoft.sqlserver.jdbc.SQLServerStatement.executeCommand(SQLServerStatement.java:180) at com.microsoft.sqlserver.jdbc.SQLServerStatement.executeStatement(SQLServerStatement.java:155) at com.microsoft.sqlserver.