title: How can a reset the contents of a List or a Map?
body: <p>If I create an object then put that object into a List or Map, then will setting that object to null affect the content of List and Map?</p>
  
  <p>like:</p>
  
  <pre><code>Object obj = new Object();
  List&lt;Object&gt; list = new ArrayList&lt;Object&gt;();
  Map&lt;Integer, Object&gt; map = new HashMap&lt;Integer, Object&gt;();
  
  list.add(obj);
  map.put(1, obj);
  
  obj = null;
  </code></pre>
  
  <p>now after this line if I want the contents in list and map both be null, is it possible?
  if not, is it achievable? How?</p>