I have tried to compile a simple java program from
tutuorial:

class HelloWorldApp {
            public static void main(String[] args) {
                System.out.println("Hello World!"); }
        }

It has compiled OK with "javac HelloWorldApp.java"
and resulted a class file HelloWorldApp.class
I wanted to run this class file with the following command:
"java HelloWorldApp.class" , but instead of HelloWorld
message I got the following:

[root@paul /root]# java HelloWorldApp.class
java.lang.NoClassDefFoundError: HelloWorldApp/class
        at java/lang/Throwable.<init>(37)
        at java/lang/Error.<init>(21)
        at java/lang/LinkageError.<init>(21)
        at java/lang/NoClassDefFoundError.<init>(21)