JAVA DATA TYPES

BASIC JAVA PROGRAMMING LANGUAGE TYPES 

 

The Java programming language has many built in data types.These fall into two broad categories:

• class types
• primitive types

Primitive types are aimple values,are not objects.Class types are used for more complex types, including all of the types.Class types are used to create objects.

Primitive  Types

Java programming language defines eight primitive data types, which can be considered in 4 categories:

• Logical-boolean
• Texual-char
• Integral-byte,short,int and long
• Floating point-double and float

Logical -boolean

• Logical values are represented using the boolean type,which takes either true or false.It has two literal values:true and false.

Textual-char

• Single characters represented by using the char type.A char represents a 16-bit, unsigned Unicode character.Single character must enclose a character literal in single quotes(' ').

Example:

'b' The letter b

Texual-String

• It is not a primitive but a class, to represent sequences of characters.String literals enclosed in double quotes("").

Primitive data types.

A primitive type is predefined by the language and is named by a reserved keyword. Primitive values do not share state with other primitive values. The eight primitive data types supported by the Java programming language are:

 

• byte: The byte data type is an 8-bit signed two's complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive). The byte data type can be useful for saving memory in large arrays, where the memory savings actually matters. They can also be used in place of int where their limits help to clarify your code; the fact that a variable's range is limited can serve as a form of documentation.
•  short: The short data type is a 16-bit signed two's complement integer. It has a minimum value of -32,768 and a maximum value of 32,767 (inclusive). As with byte, the same guidelines apply: you can use a short to save memory in large arrays, in situations where the memory savings actually matters.
• int: The int data type is a 32-bit signed two's complement integer. It has a minimum value of -2,147,483,648 and a maximum value of 2,147,483,647 (inclusive). For integral values, this data type is generally the default choice unless there is a reason (like the above) to choose something else. This data type will most likely be large enough for the numbers your program will use, but if you need a wider range of values, use long instead.
• long: The long data type is a 64-bit signed two's complement integer. It has a minimum value of -9,223,372,036,854,775,808 and a maximum value of 9,223,372,036,854,775,807 (inclusive). Use this data type when you need a range of values wider than those provided by int.
• float: The float data type is a single-precision 32-bit IEEE 754 floating point. As with the recommendations for byte and short, use a float (instead of double) if you need to save memory in large arrays of floating point numbers. This data type should never be used for precise values, such as currency. For that, you will need to use the java.math.BigDecimal  class instead. Numbers and Strings covers BigDecimal and other useful classes provided by the Java platform.
• double: The double data type is a double-precision 64-bit IEEE 754 floating point. Its range of values is beyond the scope of this discussion. For decimal values, this data type is generally the default choice. As mentioned above, this data type should never be used for precise values, such as currency.
• boolean: The boolean data type has only two possible values: true and false. Use this data type for simple flags that track true/false conditions. This data type represents one bit of information, but its "size" isn't something that's precisely defined.
• char: The char data type is a single 16-bit Unicode character. It has a minimum value of '\u0000' (or 0) and a maximum value of '\uffff' (or 65,535 inclusive).

In addition to the eight primitive data types listed above, the Java programming language also provides special support for character strings via the java.lana.String class. Enclosing your character string within double quotes will automatically create a new String object; for example, String s = "this is a string";. String objects are immutable, which means that once created, their values cannot be changed. The String class is not technically a primitive data type.

Default Values

The following chart summarizes the default values for the above data types.

Data Type	Default Value (for fields)
byte	0
short	0
int	0
long	0L
float	0.0f
double	0.0d
char	'\u0000'
String (or any object)	Null
boolean	False

 

 

 Java Primitive Data Types (8)

Type	Contains	Default	Size	Range
boolean	true or false	false	1 bit	NA
char	Unicode character unsigned	\u0000	16 bits or 2 bytes	0 to 216-1 or \u0000 to \uFFFF
byte	Signed integer	0	8 bit or 1 byte	-27 to 27-1 or -128 to 127
short	Signed integer	0	16 bit or 2 bytes	-215 to 215-1 or -32768 to 32767
int	Signed integer	0	32 bit or 4 bytes	-231 to 231-1 or -2147483648 to 2147483647
long	Signed integer	0	64 bit or 8 bytes	-263 to 263-1 or -9223372036854775808 to 9223372036854775807
float	IEEE 754 floating point single-precision	0.0f	32 bit or 4 bytes	�1.4E-45 to �3.4028235E+38
double	IEEE 754 floating point double-precision	0.0	64 bit or 8 bytes	�439E-324 to �1.7976931348623157E+308