java.sql.SQLException: Invalid handle
java.lang.NullPointerException
at readquestion.actionPerformed(readquestion.java:48)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:18
34)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.jav
a:2152)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel
.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258
)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonL
istener.java:234)
at java.awt.Component.processMouseEvent(Component.java:5463)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3052)
at java.awt.Component.processEvent(Component.java:5228)
at java.awt.Container.processEvent(Container.java:1961)
at java.awt.Component.dispatchEventImpl(Component.java:3931)
at java.awt.Container.dispatchEventImpl(Container.java:2019)
at java.awt.Component.dispatchEvent(Component.java:3779)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4203
)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3883)

at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3813)
at java.awt.Container.dispatchEventImpl(Container.java:2005)
at java.awt.Window.dispatchEventImpl(Window.java:1757)
at java.awt.Component.dispatchEvent(Component.java:3779)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:234)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)

at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
这些是运行捕捉的异常，望各位高手能够提出你们的解决建议,先谢了！