Core Java вопросы и ответы для интервью

Question: Difference between ClassNotFoundException and NoClassDefFoundError in Java?

Answer: Many a times we confused ourselves with ClassNotFoundException and NoClassDefFoundError, though both of them related to Java Classpath they are completely different to each other. ClassNotFoundException comes when JVM tries to load a class at runtime dynamically means you give the name of class at runtime and then JVM tries to load it and if that class is not found in classpath it throws ClassNotFoundException. While in case of NoClassDefFoundError the problematic class was present during Compile time and that's why program was successfully compile but not available during runtime by any reason. NoClassDefFoundError is easier to solve than ClassNotFoundException in my opinion because here we know that Class was present during build time.
Let me know how exactly you are facing NoClassDefFoundError and I will guide you how to troubleshoot it, if you are facing with something new way than I listed above we will probably document if for benefit of others and again don’t afraid with Exception in thread "main" java.lang.NoClassDefFoundError