prevent duplicate entry in contact list

Question

i want to enter contact list: "contact_name" , and "contact_number" into phone's contact list i used following code for that :

ArrayList<ContentProviderOperation> ops = new ArrayList<ContentProviderOperation>();
ops.add(ContentProviderOperation.newInsert(ContactsContract.RawContacts.CONTENT_URI)
   .withValue(ContactsContract.RawContacts.ACCOUNT_TYPE, null)
   .withValue(ContactsContract.RawContacts.ACCOUNT_NAME, null)
                                   .build());

//------------------------------------------------------ Names
ops.add(ContentProviderOperation.newInsert(ContactsContract.Data.CONTENT_URI)
   .withValueBackReference(ContactsContract.Data.RAW_CONTACT_ID, 0)
   .withValue(ContactsContract.Data.MIMETYPE,     ContactsContract.CommonDataKinds.StructuredName.CONTENT_ITEM_TYPE)
   .withValue(ContactsContract.CommonDataKinds.StructuredName.DISPLAY_NAME, name).build());
//------------------------------------------------------ Mobile Number
ops.add(ContentProviderOperation.newInsert(ContactsContract.Data.CONTENT_URI)
   .withValueBackReference(ContactsContract.Data.RAW_CONTACT_ID, 0)
   .withValue(ContactsContract.Data.MIMETYPE,  ContactsContract.CommonDataKinds.Phone.CONTENT_ITEM_TYPE)
   .withValue(ContactsContract.CommonDataKinds.Phone.NUMBER, phone)
   .withValue(ContactsContract.CommonDataKinds.Phone.TYPE, 
ContactsContract.CommonDataKinds.Phone.TYPE_MOBILE)
                                       .build());


                        // Asking the Contact provider to create a new
                        // contact

                               try 
                               {
                                   getContentResolver().applyBatch(ContactsContract.AUTHORITY, ops);
                               } 
                               catch (Exception e) 
                               {               
                                   e.printStackTrace();
                                   Toast.makeText(getApplicationContext(), "Exception: " + e.getMessage(), Toast.LENGTH_SHORT).show();
                               }

it run successfully, but i want to prevent insertion of duplicate entry,

for that i have used below link but could not find out proper solution

contact exists in contacts