Query Contacts database for contacts with phone number only

Last exercise "Query Contacts database" for all contacts. If you want to query contacts with phone number only, simple change the selection:

Change:
String selection = ContactsContract.Contacts.DISPLAY_NAME + " IS NOT NULL";

to:
String selection = ContactsContract.Contacts.HAS_PHONE_NUMBER + "=1";

Query Contacts database for contacts with phone number only