title: Which java collection allows duplicate keys
body: <p>Im trying to write program to remove duplicate key-value pairs of a word list. However if key is duplicated with different value, that record should be allowed to add. Please help me to understand Which java collection would be solve this situation.</p>
  
  <ul>
  <li>key1  aaaa</li>
  <li>key2  bbbb</li>
  <li>key3  cccc</li>
  <li>key4  dddd</li>
  <li>key2  bbbb - duplicate pair - not allowed </li>
  <li>key1  hhhh - duplicate key - allowed </li>
  <li>key5  gggg</li>
  <li>key2  nnnn</li>
  </ul>