Ivor Horton's Beginning Java™ 2, JDK™ 5th Edition

Appendix A. Keywords

The following key words are reserved in Java, so you must not use them as names in your programs"

abstract	assert	boolean	break
bytet	case	catch	char
class	const	continue	default
do	double	else	enum
extends	final	finally	float
for	goto	if	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

You should also not attempt to use the boolean values true and false or null as names in your programs