realm

realm.java

classpath "io.realm:realm-gradle-plugin:5.3.0"
apply plugin: 'realm-android'

realm {
    syncEnabled = true;
}





public class RealmActivity extends AppCompatActivity implements View.OnClickListener {
    Realm realm;
    Button button;
    EditText editText;
    String s = "";
    TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_realm);
        button = findViewById(R.id.button);
        editText = findViewById(R.id.editText);
        textView = findViewById(R.id.textView);
        button.setOnClickListener(this);
        Realm.init(this);
        realm = Realm.getDefaultInstance();
        read();

    }

    @Override
    protected void onDestroy() {
        realm.close();
        super.onDestroy();
    }

    private void read() {
        textView.setText("");

        RealmResults<RealmObjectName> results = realm.where(RealmObjectName.class).findAll();

        for (RealmObjectName name : results) {
            s += name.getName() + "\n";
        }
        textView.setText(s);
        recyclerAdapter.notifyDataSetChanged();


    }

    public void writeToDIsk() {
        realm.beginTransaction();
        RealmObjectName nameRealmObject = realm.createObject(RealmObjectName.class);
        nameRealmObject.setName(editText.getText().toString());
        realm.commitTransaction();
    }
    
    //or
        public void writeToDIsk() {
        realm.executeTransaction(new Realm.Transaction() {
            @Override
            public void execute(Realm realm) {
                realm.createObject(RealmObjectName.class).setName(editText.getText().toString());
            }
        });
    }
     public void deleteFromDatabase(final int index){
       realm.executeTransaction(new Realm.Transaction() {
           @Override
           public void execute(Realm realm) {
               RealmResults<Model> result = realm.where(Model.class).findAll();
               result.deleteFromRealm(index);
               readDiskData();

           }
       });
    }

    @Override
    protected void onStart() {
        super.onStart();

    }

    @Override
    public void onClick(View v) {
        if (editText.getText().toString().length() > 0) {
            writeToDIsk();
        } else {
            Toast.makeText(this, "Type something..", Toast.LENGTH_SHORT).show();
        }
        editText.setText("");
        read();
    }
}


//////

public class RealmObjectName extends RealmObject {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}