在Eclipse中执行Project-> Clean ...解决了这个问题。

I have a Java project in Eclipse perfectly running smoothly until this afternoon, when I updated some files (including a ant build.xml file). When I build the project, the following error appears:

java.lang.NoClassDefFoundError: proj/absa/FrontEnd/ApplicationStarter
Caused by: java.lang.ClassNotFoundException: proj.absa.FrontEnd.ApplicationStarter
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source) at
    java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)  
Exception in thread "main" 

Does anyone have a clue where the problem may be?

Doing Project->Clean… in Eclipse solved this problem for me.