ClassNotFoundException is a nightmare for developers regardless on their java experience. java.lang.ClassNotFoundException occurs because a particular java class cannot be found. Simple enough, there's many reasons why this may be the case.

Don't get confused with the exceptions ClassNotFoundException and NoClassDefFoundError because they are completely different.

As the name suggests, the JVM cannot find/locate a particular class when it loads a particular class and references another class. The JVM doesn't go searching for a particular class, YOU tell the class where it can be located. This is called the ClassPath.

You're basically stating to the JVM that alllll the classes that it'll will need can be located within the classpath. The classpath can be a single directory for the JVM to lot into, or it could contain many addresses of specific classes which is all rolled into one. The classpath can be assigned as a global value, so everyone can use it, or it can be executed at the time of the JVM execution.

classpath. Another important point about this Exception is that, It is a checked Exception and you need to provide explicitly Exception handling while using methods which can possibly throw classnotfoundexception in java either by using try-catch block or by using throws clause. Though underlying concept of this exception is simple but it always manifest itself in such format that you need to spend some time to figure out what exactly wrong with your classpath. If you want to know nasty secrets of java classpath which can cause issue see the link.

Read more: http://javarevisited.blogspot.com/2011/08/classnotfoundexception-in-java-example.html#ixzz2gUfHc318

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