How to check if an application is installed in Android system

See if an application is installed

// If no resource for the given package exists, this package is not installed in the phone

try {
    mGenieResources = getPackageManager().getResourcesForApplication(GENIE_PACKAGE_ID);
} catch (PackageManager.NameNotFoundException e) {
    // no weather info available
    Log.w(LOG_TAG, "Can't find "+GENIE_PACKAGE_ID+". Weather forecast will not be available.");
}