Java：Exception in thread “main“ java.lang.NoClassDefFoundError: IOException

出现下面的问题

Exception in thread "main" java.lang.NoClassDefFoundError: IOException
	at java.lang.Class.getDeclaredMethods0(Native Method)
	at java.lang.Class.privateGetDeclaredMethods(Unknown Source)
	at java.lang.Class.privateGetMethodRecursive(Unknown Source)
	at java.lang.Class.getMethod0(Unknown Source)
	at java.lang.Class.getMethod(Unknown Source)
	at sun.launcher.LauncherHelper.validateMainClass(Unknown Source)
	at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)
Caused by: java.lang.ClassNotFoundException: IOException
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	... 7 more

改完之后就可以了。