title: HashMap<String, boolean> copy all the keys into HashMap<String, Integer>and initialize values to zero
body: <p>What is the best way ?</p>
  
  <p>Just looping through and putting the key and zero, or is there another more elegant or existing library method. I am also using Google's guava java library if that has any useful functionality ?</p>
  
  <p>Wanted to check if there was anything similar to the copy method for lists, or Map's <a href="http://download.oracle.com/javase/1.4.2/docs/api/java/util/Map.html#putAll%28java.util.Map%29" rel="noreferrer">putAll</a> method, but just for keys.</p>