Data Types of JAVA

Data Types of JAVA
 To represent data values in your code you use literals. Literals are described by types, named by identifiers, and stored in variables, which were outlined earlier in the chapter and are explored further in this section.
When you use literals in your code, they appear in their raw form rather than as a result of an expression. Several types of literals are commonly used: numbers, integers, floating points, characters, Booleans, and strings.
Table 1.1 outlines Java's strict definitions of these data types.

Table 1.1. Rules for Java literals.

Literal Type	Typename	Rule
Number	Num	Can_ be integer, floating point, or character.
Integer		Can be decimal, hexadecimal, or octal.
	Byte	8-bit integers between -128 and 127.
	Short	16-bit integers between -32768 and 32767.
	Int	32-bit integers between -2147483648 and 2147483647.
	Long	64-bit integers between -9223372036854775808 and 9223372036854775807 or have L or l appended to them.
	Hex	Preceded by 0x or 0X.
	Oct	Preceded by 0.
Floating point		Any number with a decimal point. Can be made exponential by appending an e or E, followed by the exponent.
	Float	32-bit.
	Double	64-bit.
Character	Char	16-bit integers represented by a single character and enclosed in single quotes.
		In Java, the Unicode character map is used. The following special characters must be represented by escape sequences:
		backspace      \b
		backslash       \\
		carriage return  \r
		double quote   \"
		formfeed        \f
		hex number     \xhh
		horizontal tab   \t
		newline         \n
		octal number    \000
		question mark  \q
		single quote     \'
		vertical tab      \v
Boolean	Boolean	Can only be true or false. Are not represented by 0 or 1.
String	String	Zero or more characters enclosed in double quotes.

Literals are described by identifiers. Identifiers are sequences of letters and digits, and can also be used to describe variables, methods, and classes. Identifiers can consist of any letter from a to z, underscore, dollar sign, digits from 0 to 9 (except as the first character); identifiers are case-sensitive.
Java has several reserved keywords that are its own identifiers, which cannot be used as identifiers in any way other than that defined by Java, as listed in Table 1.2. Though these words are reserved, not all are used in the most recent release.


Table 1.2. Reserved keywords.

Abstract	else	int	short
boolean	extends	interface	static
break	final	long	super
byte	finally	native	switch
case	float	new	synchronized
cast	for	null	this
catch	future	operator	throw
char	generic	outer	throws
class	goto	package	transient
const	if	private	try
continue	implements	protected	var
default	import	public	void
do	inner	rest	volatile
double	instanceof	return	while