Java's keywords are reserved and cannot be used as names in your Java programs. Neither can reserved words true, false, and null.

JavaTM Language Keywords
abstract	else	interface	super
boolean	extends	long	switch
break	final	native	synchronized
byte	finally	new	this
case	float	package	throw
catch	for	private	throws
char	if	protected	transient
class	implements	public	try
continue	import	return	void
default	instanceof	short	volatile
do	int	static	while
double