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If you get errors, please post them here.

Have you tried executing the java command when you are in the JAVA folder?
Read post#9 again

What folder is the simple.class file in? Use the dir command to show what files are in the current folder.
If the simple.class file is NOT in your current folder, then the java command will not find...

Use the cd command to change directories.
cd THEDIR
or cd ..

But you are in a different folder, not the one with the simple.class file. Here you are in the Scotty folder:

Change folders using the cd command to be in the Java folder, not the Scotty folder.

Where is the .class file created by the javac command? Is it in the same folder where you executed the java command?
You told the javac command where the source file was.