title: "Left join" of two different Java objects
body: <p>I have a list of Object1 (<code>List&lt;Object1&gt;</code>) and a list of Object2 (<code>List&lt;Object2&gt;</code>)</p>
  
  <ul>
  <li>Object 1 has multiple properties, including <code>id</code></li>
  <li>Object 2 has multiple properites, including <code>object1id</code></li>
  </ul>
  
  <p>I have some SQL background and what I'm trying to do is to perform a "left join" on</p>
  
  <p><code>object1.id = object2.object1id</code></p>
  
  <p>This would result in a <code>List&lt;Object3&gt;</code> that represents the left join.
  I could hardcode an algorithm in Java (for... for...), but I'm sure this wouldn't be efficient with at least a complexity of n*m. </p>
  
  <p>Do you have a better solution? (with code if possible, thanks!)</p>