Java Buzz Forum - NoClassDefFoundError vs ClassNotFoundExcepiton in Java

Both NoClassDefFoundError and ClassNotFoundException are dreaded Error which comes when JVM or ClassLoader not able to locate class during class loading process. Since different ClassLoader loads classes from different location, sometime this issue may caused because of incorrect CLASSPATH as well i.e. some JAR files from lib is mission or from old version. Though look quite similar there is subtle difference between NoClassDefFoundError and ClassNotFoundException, NoClassDefFoundError indicates that class was present during time of compilation but not available when you run Java program, some time error on static initializer block can also result in NoClassDefFoundError. On the other hand ClassNotFoundException is nothing to do with compile time, ClassNotFoundException comes when you try to load a class in runtime using Reflection, e.g. loading SQL drivers and corresponding Class loader is not able to find this class. Apart from this fundamental difference between NoClassDefFoundError and ClassNoFoundException in Java, let's see some more points for better understanding.


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