title: How to implement nested classes in objective-c like Java?
body: <p>I need to implement nested  classes. How do I write it in objective-c?<br />
  For example, I have such code:</p>
  
  <pre><code>public class A {
      private int a;
      private B b;
  
      class B {
          private int z;
          public void f() {
              a = 1;
          }
      }
  
      public void fA() {
          b.f();
      }
  }
  </code></pre>
  
  <p>How can I implement this code in objective-c??</p>