title: Java compare two map
body: <p>In java, I want to compare two maps, like below, do we have existing API to do this ?</p>
  
  <p>Thanks</p>
  
  <pre><code>Map&lt;String, String&gt; beforeMap ;
  beforeMap.put("a", "1");
  beforeMap.put("b", "2");
  beforeMap.put("c", "3");
  
  Map&lt;String, String&gt; afterMap ;
  afterMap.put("a", "1");
  afterMap.put("c", "333");
  
  //--- it should give me:
  b is missing, c value changed from '3' to '333'
  </code></pre>