刚开始学java,在看一段比较简单的代码,原本是可以正常运行的,但是我按照自己的想法添加了一部分内容后,编译可以通过,但再运行时点击界面上的按钮却出不来想要的结果,没有任何反应。只是在命令窗口滚出一屏的错误提示来。简单的错误我还大概看得了,但是一下出了这么大段的错误提示,而且也找不到它所指的错误位置,我想是不是因为某个通用的基础性的东西我没做对呢?恳请大家指点一下。
补充说明,出现错误提示前的操作是点击某按钮,其作用为查询文件中某行数据并在页面上返回显示其值
错误提示如下:java.lang.NullPointerException
at StudentSituation.actionPerformed(StudentSituation.java:142)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:17
86)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Abstra
ctButton.java:1839)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel
.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258
)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonL
istener.java:245)
at java.awt.Component.processMouseEvent(Component.java:5100)
at java.awt.Component.processEvent(Component.java:4897)
at java.awt.Container.processEvent(Container.java:1569)
at java.awt.Component.dispatchEventImpl(Component.java:3615)
at java.awt.Container.dispatchEventImpl(Container.java:1627)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483
)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
at java.awt.Container.dispatchEventImpl(Container.java:1613)
at java.awt.Window.dispatchEventImpl(Window.java:1606)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:480)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137) at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)
补充说明,出现错误提示前的操作是点击某按钮,其作用为查询文件中某行数据并在页面上返回显示其值
错误提示如下:java.lang.NullPointerException
at StudentSituation.actionPerformed(StudentSituation.java:142)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:17
86)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Abstra
ctButton.java:1839)
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:245)
at java.awt.Component.processMouseEvent(Component.java:5100)
at java.awt.Component.processEvent(Component.java:4897)
at java.awt.Container.processEvent(Container.java:1569)
at java.awt.Component.dispatchEventImpl(Component.java:3615)
at java.awt.Container.dispatchEventImpl(Container.java:1627)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483
)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
at java.awt.Container.dispatchEventImpl(Container.java:1613)
at java.awt.Window.dispatchEventImpl(Window.java:1606)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:480)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137) at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)
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at StudentSituation.actionPerformed(StudentSituation.java:142),查查这行代码,看看值从哪取得的