problem while applying ArrayAdapter

protected String[] mAndroidNames= {
        "android beta",
        "android 1.0",
        "android 1.1",
        "cupcake",
        "donut",
        "Eclair",
        "Froyo",
        "Gingerbread",
        "Honeycomb",
        "Ice cream sandwich",
        "jellybean",
        "KITKAT",
        "Lion?"
};
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main_list);


    ArrayAdapter<String> adapter =new ArrayAdapter<String>(this , android.R.layout.simple_list_item_1, mAndroidNames);
    setListAdapter adapter;
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main_list, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}