Simple DATABASE ( ADD,DELETE,UPDATE,GET SINGLE,LIST )

---------------------MainActivity.class--------------------

public class MainActivity extends AppCompatActivity {

    private final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        DatabaseHandler db = new DatabaseHandler(this);

        // Inserting Contacts
        Log.d("Insert: ", "Inserting ..");
        /*db.addContact(new Contact(1,"Ravi", "9100000000"));
        db.addContact(new Contact(2,"Srinivas", "9199999999"));
        db.addContact(new Contact(3,"Tommy", "9522222222"));
        db.addContact(new Contact(4,"Karthik", "9533333333"));
        db.addContact(new Contact(5,"Karthik", "9533333333"));*/

        Contact contactAdd = new Contact();
        for (int i = 0; i < 10; i++) {
            contactAdd.setID(i);
            int longtime = (int) System.currentTimeMillis();
            String number = String.valueOf(longtime).substring(4);


            contactAdd.setName(number);
            contactAdd.setPhoneNumber("9834337373");
            db.addContact(contactAdd);
        }


        // Reading all contacts
        Log.d("Reading: ", "Reading all contacts..");
        List<Contact> contacts = db.getAllContacts();
        for (Contact cn : contacts) {
            String log = "Id: " + cn.getID() + " ,Name: " + cn.getName() + " ,Phone: " +
                    cn.getPhoneNumber();
            // Writing Contacts to log
            Log.d("Name: ", log);

        }
        /*...........................update_single_data................*/
        Contact contact1 = new Contact();
        contact1.setID(1);
        contact1.setName("shirsh");
        contact1.setPhoneNumber("9393938383");

        int updatePosition = db.updateContact(contact1);
        Log.v(TAG, "updatePosition  :   " + updatePosition);
        /*...........................get_single_data................*/
        Contact contact = db.getContact(1);
        contact.getID();
        contact.getName();
        contact.getPhoneNumber();

        Log.v(TAG, "Data :" + contact.getID() + "\n" +
                contact.getName() + "\n" + contact.getPhoneNumber());

        /*..........................delete_single_data...................*/

        Contact contact2 = new Contact();
        contact2.setID(5);
        db.deleteContact(contact2);
    }
}

------------------Contact.class-------------

public class Contact {

    int _id;

    String _name;

    String _phone_number;

    public Contact(){   }

    public Contact(int id, String name, String _phone_number){

        this._id = id;

        this._name = name;

        this._phone_number = _phone_number;

    }

    public Contact(String name, String _phone_number){

        this._name = name;

        this._phone_number = _phone_number;

    }

    public int getID(){

        return this._id;

    }

    public void setID(int id){

        this._id = id;

    }

    public String getName(){

        return this._name;

    }

    public void setName(String name){

        this._name = name;

    }

    public String getPhoneNumber(){

        return this._phone_number;

    }

    public void setPhoneNumber(String phone_number){

        this._phone_number = phone_number;

    }

}

---------------DatabaseHandler.class---------

public class DatabaseHandler extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;

    private static final String DATABASE_NAME = "contactsManager";

    private static final String TABLE_CONTACTS = "contacts";

    private static final String KEY_ID = "id";

    private static final String KEY_NAME = "name";

    private static final String KEY_PH_NO = "phone_number";

    public DatabaseHandler(Context context) {

        super(context, DATABASE_NAME, null, DATABASE_VERSION);

        //3rd argument to be passed is CursorFactory instance

    }

    // Creating Tables

    @Override

    public void onCreate(SQLiteDatabase db) {

        String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS + "("

                + KEY_ID + " INTEGER PRIMARY KEY," + KEY_NAME + " TEXT,"

                + KEY_PH_NO + " TEXT" + ")";

        db.execSQL(CREATE_CONTACTS_TABLE);

    }

    // Upgrading database

    @Override

    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        // Drop older table if existed

        db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);

        // Create tables again

        onCreate(db);

    }

    // code to add the new contact

    void addContact(Contact contact) {

        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();

        values.put(KEY_NAME, contact.getName()); // Contact Name

        values.put(KEY_PH_NO, contact.getPhoneNumber()); // Contact Phone

        // Inserting Row

        db.insert(TABLE_CONTACTS, null, values);

        //2nd argument is String containing nullColumnHack

        db.close(); // Closing database connection

    }

    // code to get the single contact

    Contact getContact(int id) {

        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,

                        KEY_NAME, KEY_PH_NO }, KEY_ID + "=?",

                new String[] { String.valueOf(id) }, null, null, null, null);

        if (cursor != null)

            cursor.moveToFirst();

        Contact contact = new Contact(Integer.parseInt(cursor.getString(0)),

                cursor.getString(1), cursor.getString(2));

        // return contact

        return contact;

    }

    // code to get all contacts in a list view

    public List<Contact> getAllContacts() {

        List<Contact> contactList = new ArrayList<Contact>();

        // Select All Query

        String selectQuery = "SELECT  * FROM " + TABLE_CONTACTS;

        SQLiteDatabase db = this.getWritableDatabase();

        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list

        if (cursor.moveToFirst()) {

            do {

                Contact contact = new Contact();

                contact.setID(Integer.parseInt(cursor.getString(0)));

                contact.setName(cursor.getString(1));

                contact.setPhoneNumber(cursor.getString(2));

                // Adding contact to list

                contactList.add(contact);

            } while (cursor.moveToNext());

        }

        // return contact list

        return contactList;

    }

    // code to update the single contact

    public int updateContact(Contact contact) {

        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();

        values.put(KEY_NAME, contact.getName());

        values.put(KEY_PH_NO, contact.getPhoneNumber());

        // updating row

        return db.update(TABLE_CONTACTS, values, KEY_ID + " = ?",

                new String[] { String.valueOf(contact.getID()) });

    }

    // Deleting single contact

    public void deleteContact(Contact contact) {

        SQLiteDatabase db = this.getWritableDatabase();

        db.delete(TABLE_CONTACTS, KEY_ID + " = ?",

                new String[] { String.valueOf(contact.getID()) });

        db.close();

    }

    // Getting contacts Count

    public int getContactsCount() {

        String countQuery = "SELECT  * FROM " + TABLE_CONTACTS;

        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.rawQuery(countQuery, null);

        cursor.close();

        // return count

        return cursor.getCount();

    }

}