title: How to Convert a Map<String, List<String>> to Map<String, String> in java 8 functional APIs
body: <p>I have a map like bellow,</p>
  
  <pre><code> [key = "car", value = ["bmw", "toyota"]]
   [key = "bike", value = ["honda", "kawasaki"]]
  </code></pre>
  
  <p>I want to convert it to another map using java 8 functional apis like bellow, </p>
  
  <pre><code> [key = "bmw", value = "car"]
   [key = "toyota", value = "car"]
   [key = "honda", value = "bike"]
   [key = "kawasaki", value = "bike"]
  </code></pre>