A keyword is a special word. Its meaning is defined by the Java programming language. You cannot use these words as identifiers.
All keywords are in lowercase.
Like everything else in Java, keywords are case sensitive. For example, if you
use For with uppercase f instead of for with lowercase f it is an error.
The program shown in the first example
uses four keywords.
* public
* class
* static and
* void
In Java there are 51 keywords. They’re listed in alphabetical order here.
| abstract | assert | boolean | break | byte |
| case | catch | char | class | const |
| continue | default | do | double | else |
| enum | extends | final | finally | float |
| for | if | goto | implements | import |
| instanceof | int | interface | long | native |
| new | package | private | protected | public |
| return | short | static | strictfp | super |
| switch | synchronized | this | throw | throws |
| transient | try | void | volatile | while |
| _ (underscore) |
Some words are sometimes, incorrectly, assumed as keywords. In any case, they’re reserved in the same way as keywords.
const and goto are reserved. They are not used.true and false are not keywords. They are boolean literals.null is not a keyword. It indicates the null literal.var is not a keyword. It is a special identifier.