Android : How to change option menu icon in the action bar?

How to change the index icon of option menu?

I mean icon (3).

Here is my code:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.options, menu);

    return true;
}

And here is the XML file:

<item android:id="@+id/Bugreport"
    android:title="@string/option_bugreport" />

<item android:id="@+id/Info"
    android:title="@string/option_info" />

<item android:id="@+id/About"
    android:title="@string/option_about" />