title: read and write data with GSON
body: <p>I am struggling to find a good example on how to read and write data in my android app using GSON. Could someone please show me or point me to a good example? I am using this for data persistence between activities.</p>
  
  <p>My professor gave this example to for writing:</p>
  
  <pre><code>Vector v = new Vector(10.0f, 20.0f);
  Gson gson = new Gson();
  String s = gson.toJson(v);
  </code></pre>
  
  <p>How would I go about saving that to a file?</p>