I'm assuming you're using XML layout.

<TextView  
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:gravity="center"
    android:text="@string/**yourtextstring**"
/>

You can also use gravity center_vertical or center_horizontal according to your need.

and as @stealthcopter commented in java: .setGravity(Gravity.CENTER);