Keywords are reserved as core building blocks of the Java language.  You may not use them for names of things you create, like field and method identifiers.  The Java compiler recognizes these words (and special characters, termed operators and separators).  They direct the composition of the bytecode (executable) version of your program.

Data Building Blocks (Built-In Types)

• byte, short, int, long
• boolean
• char
• float, double

• break
• continue
• do, while
• for
• if, else
• switch, case, default
• throw
• try, catch, finally

• class
• extends
• implements
• instanceof
• interface
• new
• super, this

• return
• void

• abstract
• private, public, protected
• final
• static
• throws

• import
• package

• native
• synchronized
• transient
• volatile