在NetBeans中，当我想运行我的项目时，我按下“运行项目”按钮。 几分钟前，我意外地按下了“清洁和构建”按钮。从那一刻起，每当我按下“运行项目”按钮时，我都会收到以下错误消息，而且我无法运行我的代码！
Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError:
interactivedialign/Alignment
at interactivedialign.AliForm.(AliForm.java:254)
at interactivedialign.AliForm$8.run(AliForm.java:545)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:226)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:647)
at java.awt.EventQueue.access$000(EventQueue.java:96)
at java.awt.EventQueue$1.run(EventQueue.java:608)
at java.awt.EventQueue$1.run(EventQueue.java:606)
at java.security.AccessController.doPrivileged(Native Method)
etc..
如何解决此错误？