code: public static boolean launchOrDownloadApp(String applicationId) {
  		boolean isAppInstalled = isAppInstalled(applicationId);
  		if (isAppInstalled) {
  			launchExternalApp(applicationId);
  		} else {
  			GooglePlayUtils.launchAppDetails(applicationId);
  		}
  		return isAppInstalled;
  	}
docs: Launch applicationId app or open Google Play to download.
  
  @param applicationId
  @return true if app is installed, false otherwise.