title: Java find all the key with specific value
body: <p>is there a way to find out all the key which having same value in the map.
  Like</p>
  
  <pre><code>map.put("A","Abc");
  map.put("B","Abc");
  map.put("C","Abc"); 
  map.put("D","Bcd");
  </code></pre>
  
  <p>Here I want to find out all the key which having value "Abc".</p>