title: HashMap value change after "get"
body: <p>I have a </p>
  
  <pre><code>private Map&lt;String,List&lt;ProductScheme&gt;&gt; discountMap = new HashMap&lt;String,List&lt;ProductScheme&gt;&gt;();
  </code></pre>
  
  <p>now if i get list from <code>discountMap</code> and add an item in list
  will i have to put the list again in <code>discount map</code> or it will not be required ??</p>