java.lang.NoClassDefFoundError: org/dom4j/DocumentException [Solution]

Exception in thread "main" java.lang.NoClassDefFoundError: org/dom4j/DocumentException comes when your program is using DOM4j library but necessary JAR is not present. This error can also come when you are indirectly using DOM4j library e.g. when you use Apache POI library to read XLSX file in Java,  this library needs dom4j.jar in your classpath. Not just this one but there are several other libraries which use this JAR internally, if you are using any of them but don't have this JAR then your program will compile fine but fail at runtime because JVM will try to load this class but will not be able to find it on the classpath. Some curious developers might ask, why it didn't fail during compile time if JAR was not present there? Well, the reason for that is that your code might not be using any class file directly from the dom4j.jar file.

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