title: What is a key object (use in hashmap)?
body: <p>Could someone explain what exactly a key object is for use in hashmap? There is a method: 
  "put(Object key, Object value) 
            Associates the specified value with the specified key in this map."</p>
  
  <p>so is the key just any object you want? And by value do they mean another object or like a attribute.
  Just need some further explanation as I am confused! Thanks a bunch</p>