===== Global Constants =====
There seem to be a couple of ways to skin this cat but one way would be:
==== Add to BuildConfig ====
Example adding TAG ''DPF''

In ''build.gradle'' //the module not the project//
<code>
buildTypes {
        release {
            ...
            buildConfigField "String", "TAG","\"DPF"\""
        }
        debug {
            ...
            buildConfigField "String", "TAG", "\"DPF\""
        }
    }
</code>

  * Then rebuild the project. Check the generated ''BuildConfig'' in the Java (generated) folder.
  * You should see something like ''public static final String TAG = "DPF";''
  * Now use ''BuildConfig.TAG'' wherever you want to use the constant