What causes and what are the differences between NoClassDefFoundError and ClassNotFoundException?

Question

What is the difference between NoClassDefFoundError and ClassNotFoundException?

What causes them to be thrown? How can they be resolved?

Answer 1

NoClassDefFoundError is a linkage error basically. It occurs when you try and instantiate an object (statically with "new") and it's not found when it was during compilation.

ClassNotFoundException is more general and is a runtime exception when you try to use a class that doesn't exist. For example, you have a parameter in a function accepts an interface and someone passes in a class that implements that interface but you don't have access to the class. It also covers case of dynamic class loading, such as using loadClass() or Class.forName().