Call reference of an object as a parameter in another method
<p>For example:</p>

<pre><code>A a = new A(b);
B b = new B(a);
</code></pre>

<p>How can I use <code>b</code> as a parameter in <code>A</code> constructor when it's not existed, how can the compiler will know that <code>b</code> will be created later? </p>

<p>Thank you.</p>
