MainActivity.java

public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        recyclerView.setLayoutManager(new GridLayoutManager(this, 3));
        
        recyclerView.setAdapter(new GridLettersAdapter());
        recyclerView.setHasFixedSize(true);
        recyclerView.addItemDecoration(new GridDecoration(this));
    }

}