错误：无法找到或加载主 class (java.lang.NoClassDefFoundError) Ubuntu 18.04

Question

Using the ls commmand, I can clearly see both the.java file and the.class file of my main class created from compilation. However, when I try to run it, the Ubuntu terminal says that the class was not found. Here's a screenshot of my terminal

And here's a snippet of my main class

Any answers?

Answer 1

You haved a class inside package. So you should run your class in /home/se folder and use command java cs3421_emul.cs3421_emul

Answer 2

Since your classes are in a package your compiled classes should in the proper folder structure.

To compile the classes to proper package folders use -d. switch while compiling.

javac -d . *.java

The above command will create folders based on the package of the classes. for example you class3421_emul has a package class3421_emul so it will be compiled to class3421_emul folder.

Then run the class using java class3421_emul.class3421_emul