How "reject" instancing a class
<p>For example,</p>

<pre><code>public class Test {
    Test() {
    if(xxx)//do some check here
        //reject instancing class test.
    }
}
</code></pre>

<p>I think I can throw a exception to reject it, is there any other way?
I am not sure what's the effect of instancing been rejected, but I think a natural way is:</p>

<pre><code>Test test = new Test();//return null here indicating instancing rejected.
</code></pre>

<p>I expect java and C++ all should have this "reject" feature.</p>
