[英]Exception in thread “AWT-EventQueue-0” java.lang.NullPointerException For Loops
I have a problem with the for loop because of the nullpointerexception error. 由于nullpointerexception错误,for循环出现问题。
for (int num = 0; num < checkingAcct.getSize(); num++)
And the error comes up as: 错误出现为:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at application2.Panel.listTransactions(Panel.java:152)
at application2.Application2$Application2a.actionPerformed(Application2.java:84)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.JToggleButton$ToggleButtonModel.setPressed(JToggleButton.java:308)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
The for loop is line 152. As for application2 line 84 for循环为第152行。至于application2的第84行
if (codee == dos)
Panel.listTransactions(); <-----
And then getSize: 然后getSize:
public int getSize(){
transSize = transList.size();
return transSize;
}
Based on google findings, NullPointerException means that I didn't initialize something. 根据google的发现,NullPointerException表示我没有初始化某些内容。 But I don't know what to intialize. 但是我不知道该如何初始化。 transSize was initialized to 0. transSize初始化为0。
Thank you~ 谢谢〜
Based on the error happening at the for loop, I suspect that your checkingAcct
is null
. 基于在for循环中发生的错误,我怀疑您的checkingAcct
为null
。 Make sure you are using the constructor to initialize: 确保使用构造函数进行初始化:
CheckingAccount checkingAcct = new CheckingAccount();
. 。
If you're already doing that, make sure that it's not being assigned to null anywhere else in your code. 如果已经在执行此操作,请确保未在代码中的其他任何位置将其分配为null。
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