4.1 Primitive Data Types in Java

Data type defines a set of permitted values on which the legal operations can be performed.
In java, all the variables needs to be declared first i.e. before using a particular variable, it must be declared in the program for the memory allocation process. Like

 int pedal = 1;

This statement exists a field named "pedal" that holds the numerical value as 1. The value assigned to a variable determines its data type, on which the legal operations of java are performed. This behavior specifies that, Java is a strongly-typed programming language.

The data types in the Java programming language are divided into two categories  and can be explained using the following hierarchy structure :

•  Primitive Data Types 
•  Reference Data Types

Primitive Data Types

 The primitive data types are predefined data types, which always hold the value of the same data type, and  the values of a primitive data type don't share the state with other primitive values. These data types are named by a reserved keyword in Java  programming language.

There are eight primitive data types supported by Java programming language :

 byte
The byte data type is an 8-bit signed two's complement integer. It ranges from -128 to127 (inclusive). This type of data type is useful to save   memory  in large arrays.. We can also use byte instead of int  to increase the limit of the code. The syntax of declaring a byte type variable is shown as:
 byte b = 5;

 short

 The short data type is a 16-bit signed two's complement integer. It ranges from -32,768 to 32,767. short is used to save memory in large arrays. The syntax of declaring a short type variable is shown as:
 short s = 2;

 int

  The int data type is used to store the integer values not the fraction values. It is a 32-bit signed two's complement integer data type. It ranges from -2,147,483,648 to 2,147,483,647 that is more enough to store large number in your program.  However for wider range of values use long. The syntax of declaring a int type variable is shown as:
 int num = 50;

 long

 The long data type is a 64-bit signed two's complement integer. It ranges from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807. Use this data type with larger range of values. The syntax of declaring a long type variable is shown as:
 long ln = 746;

 float

 The float data type is a single-precision 32-bit IEEE 754 floating point. It ranges from 1.40129846432481707e-45 to 3.40282346638528860e+38 (positive or negative). Use a float (instead of double) to save memory in large arrays. We do not use this data type for the exact values such as currency. For that we have to use java.math.BigDecimal class. The syntax of declaring a float type variable is:
 float f = 105.65; 
 float f = -5000.12;

 double

  This data type is a double-precision 64-bit IEEE 754 floating point. It ranges from 4.94065645841246544e-324d to 1.79769313486231570e+308d (positive or negative). This data type is generally the default choice for decimal values. The syntax of declaring a double type variable is shown as:
 double d = 6677.60;

 char

 The char data type is a single 16-bit, unsigned Unicode character. It ranges from 0 to 65,535. They are not integral data type like int, short etc. i.e. the char data type can't hold the numeric values. The syntax of declaring a char type variable is shown as:

 char caps = 'c';

 boolean

 The  boolean data type represents only two values: true and false and occupy is 1-bit in the memory. These values are keywords in Java and  represents the two boolean states: on or off, yes or no. We use boolean data type for specifying conditional statements as if, while, do, for. In Java, true and false are not the same as True and False. They are defined constants of the language. The syntax of declaring a boolean type variable is shown as:
 boolean result = true;

 The  ranges of these data types can be described with default values using the following table:

Data Type	Default Value (for fields)	Size (in bits)	Minimum Range	Maximum Range
byte	0	Occupy 8 bits in memory	-128	+127
short	0	Occupy 16 bits in memory	-32768	+32767
int	0	Occupy 32 bits in memory	-2147483648	+2147483647
long	0L	Occupy 64 bits in memory	-9223372036854775808	+9223372036854775807
float	0.0f	Occupy 32-bit IEEE 754 floating point	1.40129846432481707e-45	3.40282346638528860e+38
double	0.0d	Occupy 64-bit IEEE 754 floating point	4.94065645841246544e-324d	1.79769313486231570e+308d
char	'\u0000'	Occupy 16-bit, unsigned Unicode character		0 to 65,535
boolean	false	Occupy 1- bit in memory	NA	NA

When we declare a field it is not always essential that we initialize it too. The compiler sets a default value to the fields which are not initialized which might be zero or null. However this is not recommended. 

 Integer Data Types

  So far you would  have been  known about these data types. Now lets take an Integer data type in brief to better understand:

As we have told that an integer number can hold a whole number. Java provides four different primitive integer data types that can be defined as  byte, short, int, and long  that can store both positive and negative values. The  ranges of these data types can be described using the following table:

Data Type	Size (in bits)	Minimum Range	Maximum Range
byte	Occupy 8 bits in memory	-128	+127
short	Occupy 16 bits in memory	-32768	+32767
int	Occupy 32 bits in memory	-2147483648	+2147483647
long	Occupy 64 bits in memory	-9223372036854775808	+9223372036854775807

Examples of floating-point literals are:

0  1  123  -42000

Floating-point numbers

A floating-point number represents a real number that may have a fractional values i.e. In the floating type of variable, you can assign the numbers in an in a decimal or scientific notation. Floating-point number have only a limited number of digits, where most values can be represented only approximately. The floating-point types are float and double with a single-precision 32-bit IEEE 754 floating point and double-precision 64-bit IEEE 754 floating point respectively. Examples of floating-point literals are:

10.0003   48.9  -2000.15  7.04e12

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