![]() For example, in Java classloader works by delegation and visibility. ![]() Sometimes in complex environments, e.g., Java EE container, the offender cases may be available in classpath but not visible to the classLoader trying to load that particular class. ![]() Due to the Visibility issues between multiple Classloaders See here to learn more useful Eclipse shortcuts for Java developers.Ģ. In Eclipse, you can use shortcuts like search resource (Ctrl + R) or search type (Ctrl + T) to find which JAR file that particular class belongs to and then check if that JAR is available in the classpath or not. In short, the first step to solving "Exception in thread "main" " is to check if the offender class is available in classpath or not. Similarly, you might have seen : org/apache/xmlbeans/XmlObject which comes if you are using XMLbeans but xmlbeans-2.60.jar is not present in your classpath (see here).Īnother common one is : org/dom4j/DocumentException, which comes due to missing dom4j.jar file (see here). See here to learn more about troubleshooting this particular issue. As soon as you add that JAR into the classpath, the error goes away. The simplest reasons for this error are the missing log4j.jar file in the classpath. If the static initializer block of a class throws an Exception during loading, the class will not be available for others to use. On the other hand, NoClassDefFoundError comes when the class was available at compile time but somehow not available at runtime. For example, when you load JDBC driver using Class.forName(String classname), you will get j instead of NoClassDefFoundError. The ClassNotFoundException comes when Java tries to load a class by its binary name during runtime, and Class is not available at that time. N oClassDefFoundError in Java is also related to class loading in Java but there is a slight difference between NoClassDefFoundError and ClassNotFoundException in Java. Java Programmers often confuse between java.lang. This could be due to a missing JAR file, any permission issue, or an incorrect classpath on runtime, depending upon your environment. It's denoted by j and comes when that particular class is present during compile time but somehow not available during runtime.
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