error

Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: net/miginfocom/swing/MigLayout
	at Gui.initialize(Gui.java:67)
	at Gui.<init>(Gui.java:49)
	at Gui$1.run(Gui.java:36)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:682)
	at java.awt.EventQueue.access$000(EventQueue.java:85)
	at java.awt.EventQueue$1.run(EventQueue.java:643)
	at java.awt.EventQueue$1.run(EventQueue.java:641)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:652)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Caused by: java.lang.ClassNotFoundException: net.miginfocom.swing.MigLayout
	at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
	... 17 more