MainActivity.java

public class MainActivity extends AppCompatActivity {
    private ActionBar toolbar;
    private BottomNavigationView bottomNavigationView;
    private String[] menus ={"Latest","Favorite","Cart","Profile"};
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        toolbar = getSupportActionBar();
        bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigationview);
        bottomNavigationView.setOnNavigationItemSelectedListener(navigationItemSelectedListener);
        toolbar.setTitle(menus[0]);
    }
    
    private BottomNavigationView.OnNavigationItemSelectedListener navigationItemSelectedListener = new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()){
                case R.id.item1:
                    toolbar.setTitle(menus[0]);
                    return true;
                case R.id.item2:
                    toolbar.setTitle(menus[1]);
                    return true;
                case R.id.item3:
                    toolbar.setTitle(menus[2]);
                    return true;
                case R.id.item4:
                    toolbar.setTitle(menus[3]);
                    return true;
            }
            return false;
        };
    };
}