how to get an icon on action bar

See more:

Mobile

Android

i am trying to display an icon on action bar that will navigate to a page.
i have downloaded an icon for it, copied it in drawable folder.

code in menu .xml

<item
        android:id="@+id/action_refresh"
        android:orderInCategory="100"
        android:showAsAction="ifRoom"
        android:icon="@drawable/back"
        android:title="Back"/>/>

code in onOptionItemSelected

if (id == R.id.action_refresh) {
			Intent z=new Intent(getApplicationContext(),HomeScreen.class);
			startActivity(z);
			return true;
		}

on running the app i icon is not shown. where could the mistake be?