Have a look at View.setVisibility(View.GONE / View.VISIBLE / View.INVISIBLE).
From the API docs:
public void setVisibility(int visibility)Since: API Level 1
Set the enabled state of this view.
Related XML Attributes: android:visibilityParameters:
visibilityOne of VISIBLE, INVISIBLE, or GONE.
Note that LinearLayout is a ViewGroup which in turn is a View. That is, you may very well call, for instance, myLinearLayout.setVisibility(View.VISIBLE).
This makes sense. If you have any experience with AWT/Swing, you'll recognize it from the relation between Container and Component. (A Container is a Component.)