title: How to uniq identify a Function in Java 8
body: <p>I am asking whether I can take a function as key for a map.</p>
  
  <p>Normally, a key object for a map should have <code>hashcode</code> and <code>equal</code> methods. However,  Java <code>Function</code> is a method object, and it does not have these two methods.</p>
  
  <pre><code>Function&lt;String, String&gt; quote1 = s -&gt; "'" + s + "'";
  Function&lt;String, String&gt; quote2 = s -&gt; "'" + s + "'";
  System.out.println(quote1.equals(quote2));  //false
  </code></pre>
  
  <p>so is it possible?  If possible, any sample?  I did not get this case by google.</p>
  
  <p>If not, is there any other way to identify time-consuming <code>Function</code> execution result? 
  Thanks</p>