Java contains 53 reserved words out of which 50 are keywords out of 50 only 48 keywords are used and two keywords const and goto are not in use and 3 are literals values true
These reserved words can not be used as identifiers.

Java Keywords: keyword is a reserved word that
abstract | continue | for | new | switch |
assert | default | goto | package | synchronized |
boolean | do | if | private | this |
break | double | implements | protected | throw |
byte | else | import | public | throws |
case | enum | instanceof | return | transient |
catch | extends | int | short | try |
char | final | interface | static | void |
class | finally | long | strictfp | volatile |
const | float | native | super | while |
const and goto are not in use
strictfp added in jdk 1.2
enum added in jdk 1.5
Reference