我正在尝试从数据库中获取记录的特定值我使用AbstractTableModel在swings中创建运行时JTable但是我试图从该类的不同javaclass中触发查询。我为where子句提供条件但是我无法在其他JFrame中显示该记录.AbstractTableModel工作正常，因为我能够在我实际声明表的内部框架中检索数据..我可以将JInternalFrame中的数据转换为JFrame我试图使用getParent.add（ ）方法但它会抛出nullpointerException Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at secondproject.select_particular_field$1.actionPerformed(select_particular_field.java:84)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at javax.swing.AbstractButton$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.Window.dispatchEventImpl(Window.java:2429)
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)
答案 0 :(得分：0)
它有点模糊，但通常会抛出NPE，因为在对象不存在时调用方法。在这种情况下，当您点击按钮select_particular_field.java
但是我试图从该类
中的不同javaclass触发查询
也许这就是问题所在。在不同的类中，对象不存在/尚未创建。
希望它有所帮助