https://developer.android.com/studio/intro/keyboard-shortcuts

Ctrl  +  A
Select  All

Ctrl  +  B
Go back to the declaration

Ctrl  +  C
Copy

Ctrl  +  D
Duplicate the highlighted code

Ctrl  +  E
See recently opened files

Ctrl  +  F
Find

Ctrl  +  V
Paste

Ctrl  +  Alt  +  L
Reformat the code

Ctrl  +  P   
Parameter info

Ctrl  + shift  +  P   
Data type of the selected object

shift + F6   
Renames variables

Ctrl  +  Q
Quick documentation lookup for any part of the code

Ctrl  +  /
Comment/uncomment a block of code

Ctrl  +  X
Cut

Ctrl  +  Y
Delete the line at the cursor

Ctrl  +  Z
Undo typing

Ctrl  +  Shift  +  Z
Redo typing

Shift Shift
Search everything - including code and menus

Alt + Shift + 7
Find all usages of a highlighted identifier - Alternatively you can use:  Edit -> Find Usages