title: Java TreeMap not good enough
body: <p>I want to have a <code>Map&lt;Integer, String&gt;</code> that can be sorted out. I have tried to use a <code>TreeMap&lt;Integer, String&gt;</code> but it only stores one key per element and I want to have multiple same key elements.<br>
  For example, when I add:</p>
  
  <pre><code>map.put(1, "Daniel");
  map.put(3, "Monica");
  map.put(4, "Pinto");
  map.put(3, "Lucia");
  </code></pre>
  
  <p>and then print all elements, with the <code>TreeMap</code> it appears as:</p>
  
  <blockquote>
    <p>1 Daniel<br>
    3 Lucia<br>
    4 Pinto</p>
  </blockquote>
  
  <p>and I want it to print:</p>
  
  <blockquote>
    <p>1 Daniel<br>
    3 Monica<br>
    3 Lucia<br>
    4 Pinto</p>
  </blockquote>
  
  <p>what datatype should I use for this?</p>