No main classes found netbeans3/28/2023 If the system class loader can't find it, it throws an ClassNotFound exception If the extension class loader can't find the class, it tells the system class loader to find it If the bootstrap class loader can't find the class, it tells the extension class loader to find it If the extension class loader can't find the class, it delegates to the bootstrap class loader. If the system class loader can't find the class, it delegates to the extension class loader. If nothing is found in the cache, it delegates the finding of the class to the parent class loader. System: This loads classes defined by the application and found on the class pathĮach class loader first checks a cache to see if the requested class has already been loaded into memory. Extensions: This loads any extension classes used by the JREģ. Bootstrap class loader: This loads the standard runtime classes found in rt.jarĢ. There are 3 built-in class loaders used by the JRE at runtime:ġ. Java utilizes a delegation mechanism for loading classes at runtime. From here, class loaders are used to dynamically load (lazy load) classes as they are needed by the application. The JRE utilizes a native class loader to load the main entry point of your application. Of course, some classes must be loaded initially when your program starts. This means the language is compiled to machine code while the program is running. Unlike C++, Java is a dynamically compiled language. This means classes are loaded into memory only when they are needed. When are Classes Loaded in Java?Ĭlasses are loaded dynamically. This gives you a better understanding of why the "Could Not Find or Load Main Class" error happens. While this error is self explanatory and easy to fix, it's worth understanding how Class Loaders work behind the scenes. If you override this with the -cp argument then make sure it's accurate! Understanding the Java Error "Could Not Find or Load Main Class" By default, the class path is the current working directory ".". If your class is part of a package then you must run it from the parent directory. Make sure you are running your application from the right folder. Make sure you are running your application from the right directory If you are running your program from the CLI, make sure that you are specifying the right class name without extensions. Make sure that your IDE has the correct configuration for finding the main class/entry point of your application. Make sure your IDE is configured properly How to fix the "Could Not Find or Load Main Class" Errorġ. While the optional -cp argument allows you to specify your own class path, you can easily get the "Could not find or load main class" error if this is incorrect. Sometimes developers provide a specified path like this: java M圜lass -cp /usr/local/path The class path is where the JVM looks for classes to load into your program. If you don't run your class with the fully qualified name AND from the right directory, you will get the "Could not find or load main class" error. Let's say you define a class like this: public class M圜lass This error is thrown whenever Java can't find or load the main class of your application. Regardless, fixing the error is easy and it starts with understanding the cause: What Causes the "Could Not Find or Load Main Class" Error? Sometimes the error is specific to your IDE. Sometimes the error will occur unexpectedly. Whether you're using Gradle or Maven, Spring Boot or Kafka, chances are you've encountered this error before. This error is very common when creating new Java based projects. ClassNotFoundException: M圜lass Caused by: : M圜lass When starting your Java application, you may encounter this error: Error: Could not find or load main class M圜lass Caused by: java. Last updated on April 01 Java Could Not Find or Load Main Class
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