can not connect to jdbc database

my code is

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {

try {

Class.forName("org.apache.derby.jdbc.ClientDriver");

} catch (ClassNotFoundException ex) {

ex.printStackTrace();

}

try {

con = DriverManager.getConnection("jdbc:derby://localhost:1527/go", "go", "go");

} catch (SQLException ex) {

ex.printStackTrace();

}

this code gives me this error message

java.lang.ClassNotFoundException: org.apache.derby.jdbc.ClientDriver

at java.net.URLClassLoader$1.run(URLClassLoader.java:200)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:188)

at java.lang.ClassLoader.loadClass(ClassLoader.java:306)

at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)

at java.lang.ClassLoader.loadClass(ClassLoader.java:251)

at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)

at java.lang.Class.forName0(Native Method)

at java.lang.Class.forName(Class.java:169)

at javaapplication28.NewJApplet.jButton1ActionPerformed(NewJApplet.java:80)

at javaapplication28.NewJApplet.access$100(NewJApplet.java:20)

at javaapplication28.NewJApplet$2.actionPerformed(NewJApplet.java:47)

at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)

at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)

at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)

at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)

at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)

at java.awt.Component.processMouseEvent(Component.java:6038)

at javax.swing.JComponent.processMouseEvent(JComponent.java:3260)

at java.awt.Component.processEvent(Component.java:5803)

at java.awt.Container.processEvent(Container.java:2058)

at java.awt.Component.dispatchEventImpl(Component.java:4410)

at java.awt.Container.dispatchEventImpl(Container.java:2116)

at java.awt.Component.dispatchEvent(Component.java:4240)

at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)

at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)

at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)

at java.awt.Container.dispatchEventImpl(Container.java:2102)

at java.awt.Component.dispatchEvent(Component.java:4240)

at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)

at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)

at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)

at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

java.sql.SQLException: No suitable driver found for jdbc:derby://localhost:1527/go

at java.sql.DriverManager.getConnection(DriverManager.java:602)

at java.sql.DriverManager.getConnection(DriverManager.java:185)

at javaapplication28.NewJApplet.jButton1ActionPerformed(NewJApplet.java:88)