Question

I have a java application where main class is dependent with some other classes. I can run the application using an IDE well. But when I want to run the application from command line by locating to the main class’s class file using java mainClass, it gives me the following error [the main class name is mainClass]:

Exception in thread "main" java.lang.NoClassDefFoundError: mainClass(wrong name: mainfolder/mainClass)

    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$100(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)

Can anybody suggest me how can I run my application without using any IDE?

Answer 1

Uou need to indicate the fully qualified name. For example if MainClass is under package com.example, you should execute java com.example.MainClass

You can check more here.

From documentation:

By default, the first non-option argument is the name of the class to
be invoked. A fully-qualified class name should be used. If the -jar
option is specified, the first non-option argume nt is the name of a
JAR archive containing class and resource f iles for the application,
with the startup class indicated by the Main-Class manifest header.
The Java runtime searches for the startup class, and other classes
used, in three sets of locations: the bootstrap class path, the
installed extensions, and the user class path.