5.Declaring Fields

Declaring Fields: 

Formatting Identifiers

In the Java programming language, an identifier is a name given to a variable, class, or method. Identifiers start with a letter, underscore (_), or dollar sign ($) and valid currency symbols. Subsequent characters can be digits. Identifiers are case-sensitive and have no maximum length.

The following are valid identifiers:
1. identifier
2. userName
3. user_name
4. _sys_var1
5. $change // Legal but not encouraged

 Initializing Fields

This section addresses the initial values allocated to the fields (attributes)
of a newly created object.
 string a="name";

Java technology provides the following mechanisms for field initialization.
● Initialize using default values
● Initialize using explicit values
● Initialize using constructors

Java Language Keywords

Here is a list of keywords in the Java programming language. You cannot use any of the following as identifiers in your programs. The keywords const and goto are reserved, even though they are not currently used. true,false, and null might seem like keywords, but they are actually literals; you cannot use them as identifiers in your programs.

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

*		not used
**		added in 1.2
***		added in 1.4
****		added in 5.0

 Source : http://docs.oracle.com/javase/tutorial/java/nutsandbolts/_keywords.html