title: compiling and running packages of Java classes in command line?
body: <p>I have a <code>helloworld.java</code> in this directory structure.</p>
  
  <pre><code>    bash: ls
      com
      bash: ls com/
      stack
      bash: ls com/stack/
      prog
      bash: ls com/stack/prog/helloworld.java
  </code></pre>
  
  <p>To compile I did, <code>javac com/stack/prog/helloworld.java</code>
  but for running it I did,<code>java com.stack.prog/helloworld</code></p>
  
  <p>Why is it for compiling, the <code>/</code> are needed. but for running it <code>.</code> are needed.</p>