Switch between activities

public class MainActivity extends AppCompatActivity {
    private Button mAddButton;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mAddButton = findViewById(R.id.addButton);
        mAddButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                openAddActivity();
            } 
        });
}

    public void openAddActivity(){
       Intent intent = new Intent(this, Main2Activity.class);
       startActivity(intent);
}