Question

java报错了 以下 是什么错误？

run:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at blackgound.Zidan.paint(Zidan.java:32)
at player.Playzidan.run(Playzidan.java:33)
at blackgound.Biankuang1.paintComponent(Biankuang1.java:51)
at javax.swing.JComponent.paint(JComponent.java:1053)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5223)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1572)
at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1495)
at javax.swing.RepaintManager.paint(RepaintManager.java:1265)
at javax.swing.JComponent._paintImmediately(JComponent.java:5171)
at javax.swing.JComponent.paintImmediately(JComponent.java:4982)
at javax.swing.RepaintManager$4.run(RepaintManager.java:824)
at javax.swing.RepaintManager$4.run(RepaintManager.java:807)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:807)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:782)
at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:731)
at javax.swing.RepaintManager.access$1300(RepaintManager.java:64)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1720)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:744)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:714)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
成功构建 (总时间: 4 秒)

Answer 1

lblNewLabel 在初始化前就调用了它的方法。
lblNewLabel.setBounds(117, 143, 172, 15);
contentPane.add(lblNewLabel);
放到lblNewLabel =new JLabel( (String)comboBox.getSelectedItem());后