title: Defining inner class outside java file
body: <p>I want to create a class, <code>ClassB</code>, as inner class of <code>ClassA</code>, but I want to write down outside <code>ClassA.java</code> file.</p>
  
  <p>How can I do this?</p>
  
  <p>It will be a lot of inner class, and <code>ClassA.java</code> file will be <strong>enormous</strong>.</p>
  
  <p><strong>UPDATE</strong><br/>
  What I really want to do is define ten classes that they will be only accessible by one class. All of them are defined inside the same package.</p>
  
  <p>Thanks.</p>