title: Check parameter in Lambda Expression
body: <p>I have this code:</p>
  
  <pre><code> Function&lt;Integer, String&gt; converter = (num) -&gt; Integer.toString(num);
  </code></pre>
  
  <p>As I see here the "num" is the parameter of the function, however, if my user accidentally input a float, there will be error.
  I only create the "num" parameter in the Function code?
  How can I add an exception like <code>if(!(num instanceOf Integer)) {//throw exception}</code>. </p>