title: How to store several values to one key (java)
body: <p>I search for a datastructure, where I can store several key-value pairs.</p>
  
  <p>The data essentially looks like this:</p>
  
  <pre><code>(1 , value_1)
  (2 , value_2)
  </code></pre>
  
  <p>So I thought of using HashMap. Sadly this won't work for me, because multiple values to one key can occur.</p>
  
  <p>(In the example above:</p>
  
  <pre><code>(1 , value_2)
  </code></pre>
  
  <p>might be another entry )</p>
  
  <p>Is there any way of performantly storing this data, except creating a List with a new Object or something like this.</p>
  
  <pre><code>get(1)
  </code></pre>
  
  <p>should return value_1 and value_2 as a list or set or anything similar.</p>
  
  <p>Thanks in advance</p>