How to use spinner

MainActivity.java

public class MainActivity extends AppCompatActivity {

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

        // リスト項目を作成する
        String[] list = new String[5];
        for (int i=0; i < 5; i++) {
            list[i] = "項目" + (i+1) ;
        }

        // リスト項目をセットする
        Spinner spinner = findViewById(R.id.spinner);
        ArrayAdapter<String> adapter = new ArrayAdapter<>(
                this,
                android.R.layout.simple_spinner_dropdown_item,
                list
        );
        spinner.setAdapter(adapter);
    }
}