title: Google API authentication in Java without using environment variable
body: <p>I have set up a simple test app to interact with Google's <a href="https://cloud.google.com/natural-language/" rel="noreferrer">Natural Language API</a>. I <a href="https://cloud.google.com/natural-language/docs/common/auth#set_up_a_service_account" rel="noreferrer">created a service account</a>, and downloaded the JSON credentials. I am running on a local development machine, so I set the <code>GOOGLE_APPLICATION_CREDENTIALS</code> environment variable to point to the JSON file. To be clear, <em>this works</em>: the app successfully makes some API calls and displays the results.</p>
  
  <p>I would like to remove the dependence on the environment variable. How can I use the known location of the JSON file (or any other approach) in the application to create the <code>LanguageServiceClient</code> with those credentials?</p>