title: How to map two lists of objects by id efficiently
body: <p>I have a <code>List</code> of objects (<code>List 1</code>) that I'm looping through. Each object has an <code>id</code> string associated with it. I have another list (<code>List 2</code>) containing a different type of object. I want to map the objects in <code>List 2</code> to my <code>List 1</code> objects. <code>List 1</code> has a <code>getId()</code> function and <code>List 2</code> has a <code>getList1Id()</code> function, that gives the <code>id</code> of the object its supposed to map to in <code>List 1</code>. How do I do this in the most efficient way possible?</p>