Java Constants

• Examples of integer constants:
  354, -37, 0, 246543 (no commas).

• Examples of floating point constants:
  4.642, -0.034, 5.98e24 (mass of earth), 9.11e-31 (mass of electron)

• Examples of character constants:
  'A', 'y', '8', '*', ' ' (space), '\n' (new line).

  Here are the escape sequences:

  Escape Sequence	Meaning
  \b	backspace
  \f	form feed
  \n	line feed
  \r	carriage return
  \t	tab
  \"	double quote
  \'	single quote
  \\	backslash

• Boolean constants:
  true, false

Java Variables

• Name   Must start with a letter and consist of letters and digits. Variables are case sensitive, which means that capitalization matters. The naming convention in Java is to start a variable name with a lower case letter, and start new words within the name with a capital letter. For example: numberOfCustomers.

• Value   The binary data contained in memory. The value is interpreted according to the variable's datatype.

• Address   Location in memory where the value is stored.

• Size   The number of bytes that the variable occupies in memory.

• Datatype   The interpretation of the value. Some important datatypes are listed in the following table.

• Range   The minimum and maximum values of the variable. The range of a variable depends on its size. In general, the bigger the size in bytes, the bigger the range.

Java Primitive Datatypes

Datatype	Meaning	Size in Bytes	Min Value	Max Value	Sig. Digits
byte	Integer	1	0	255
short	Integer	2	-32,768	32,767
int	Integer	4	-2 billion	2 billion
long	Integer	8	-9.2x1018	9.2x1018
float	Floating Point	4	-3.4x1038	3.4x1038	7
double	Floating Point	8	-1.8x10308	1.8x10308	15
char	Character	2	Any Unicode character
boolean	boolean	1	false	true

Long and Float Constants

The default datatype for a floating point constant is double.
A float constant uses an F suffix: 3.14159F.

Use a narrowing cast to convert a numeric constant to byte or short.

String Objects