AndroidDebugBuild.java

// One
if(BuildConfig.DEBUG) {
  Toast.makeText(this, "Debug mode", Toast.LENGTH_SHORT).show();
}

// Two
try {
	appInfo = pacMan.getApplicationInfo(pacName, 0);
} catch (NameNotFoundException e) {
	Toast.makeText(this, "Could not find package " + pacName, Toast.LENGTH_SHORT).show();
	e.printStackTrace();
}

// Three
buildTypes {
    debug {
        buildConfigField "boolean", "SOME_VAR", "true"
    }
    release {
        buildConfigField "boolean", "SOME_VAR", "false"
    }
}

// Four
BuildConfig.SOME_VAR;