There is this feature that Eclipse had.
Assuming you are summoning the code-completion in the middle of a word, the IDE it's giving you the possibility to configure if the suggested completion is just inserted (default Android Studio behavior) or it should overwrite the entire word/expression.
Is there a similar configuration in Android Studio?
If, instead of pressing Enter to make your code completion selection, you use Tab then the code completion will overwrite what is at the caret, rather than just inserting it.