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1.5 Primitive Data Types

In previous section, we’ve discussed that all variables must first be declared before they can be used. This involves stating the variable's type and name :

int rollno = 1;

This statement tells your program that a variable named "rollno" exists, holds numerical data, and has an initial value of "1". A variable's data type determines the values it may contain, plus the operations that may be performed on it.

There are eight basic data types for the storage of integers, floating-point numbers, characters, and Boolean values. These often are called primitive types because they are built in parts of the Java language.

Integer Types

There are four data types you can use to store integers.

Type	Size	Values That Can Be Stored
byte	8 bits	-128 to 127
short	16 bits	-32,768 to 32,767
int	32 bits	-2,147,483,648 to 2,147,483,647
long	64 bits	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807

Floating-point Types

Integer can store only whole numbers, another type of number that can be stored is a floating-point number. Floating-point numbers are numbers with a decimal point.

In Java there are two data types that can represent floating-point numbers. They are float and double. The float data type is a single precision data type. It can store a floating-point number with 7 digits of accuracy.

The double data type is a double precision data type. It can store a floating-point number with 15 digits of accuracy. A float variable occupies 4 bytes of memory, whereas a double variable uses 8 bytes.

Character type

The char type is used for individual characters, such as letters, numbers, punctuation, and other symbols.

Booleans

boolean data type holds either true or false in Java.