ClassNotFoundExceptionĬlassNotFoundException is a runtime exception that is thrown when an application tries to load a class at runtime using the Class.forName() or loadClass() or findSystemClass() methods ,and the class with specified name are not found in the classpath. NoClassDefFoundError is an error that occurs when a particular class is present at compile time, but was missing at run time. However, they occur at different scenarios.ĬlassNotFoundException is an exception that occurs when you try to load a class at run time using Class.forName() or loadClass() methods and mentioned classes are not found in the classpath. and NoClassDefFoundError occur when a particular class is not found at runtime. You might be running your program using jar command and class was not defined in manifest file's ClassPath attribute.Any start-up script is overriding Classpath environment variable.Because NoClassDefFoundError is a subclass of it can also come if one of it dependency like native library may not available.
NoClassDefFoundError due to the failure of static initialization is quite common. If you are working in J2EE environment than the visibility of Class among multiple Classloader can also cause, see examples and scenario section for detailed discussion.The class is not available in Java Classpath.when your compiled class which is defined in a package, doesn’t present in the same package while loading like in the case of JApplet it will throw NoClassDefFoundError in Java.Typo on XML Configuration can also cause NoClassDefFoundError in Java.Permission issue on JAR file can also cause NoClassDefFoundError in Java.Just try to run with explicitly -classpath option with the classpath you think will work and if it's working then it's a sure short sign that someone is overriding java classpath. The class is not in Classpath, there is no sure shot way of knowing it but many times you can just have a look to print System.getproperty("java.classpath") and it will print the classpath from there you can at least get an idea of your actual runtime classpath.Ī simple example of NoClassDefFoundError is class belongs to a missing JAR file or JAR was not added into classpath or sometimes jar's name has been changed by someone like in my case one of my colleagues has changed tibco.jar into tibco_v3.jar and the program is failing with and I were wondering what's wrong.If a class was present during compile time but not available in java classpath during runtime. Java Virtual Machine is not able to find a particular class at runtime which was available at compile time. The point is, a NoClassDefFoundError is not necessarily a classpath problem. The earlier failure could be a ClassNotFoundException or an ExceptionInInitializerError (indicating a failure in the static initialization block) or any number of other problems. Usually this indicates that we previously attempted to load a class from the classpath, but it failed for some reason - now we're trying to use the class again (and thus need to load it, since it failed last time), but we're not even going to try to load it, because we failed loading it earlier (and reasonably suspect that we would fail again). This is different than saying that it could not be loaded from the classpath. This exception indicates that the JVM looked in its internal class definition data structure for the definition of a class and did not find it. This indicates that we were trying to load the class definition, and the class did not exist on the classpath. This exception indicates that the class was not found on the classpath. It is important to keep two or three different exceptions straight in our head in this case: While it's possible that this is due to a classpath mismatch between compile-time and run-time, it's not necessarily true.
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