Basic Java Language

This lesson discusses the basics of the Java language, including variables, primitives, operators, statements and Java writing conventions.

Variables

Variables are used to store data that can change. There are two main categories of variables, reference variables and primitive variables. Reference variables are place holders for objects (More on objects in Lesson 4, Java Objects and Classes.) Primitive variables are given a value of a primitive, a basic value. Variables are all given a type when they are declared, such as "integer" or "string".

Primitive Data Types

Primitives are the simplest type of data. Primitives consist of numbers, letters and strings of letters. The following table shows all the types of primitives.

Primitive	Description	Values
byte	A brief, 8-bit integer	Whole numbers -128 through 127
short	A short, 16-bit integer	Whole numbers -32,768 through 32,767
int	A 32 bit integer	Whole numbers -2,147,483,648 through 2,147,483,647
long	A long, 64 bit integer	Whole numbers -9,223,372,036,854,775,808 through 9,223,372,036,854,775,807
float	Single-percision floating poing (32-bit IEEE 754)	Smallest positive non-zero: 14e-45, Largest positive non-zero: 3.4028234e38
double	Double-percision floating point (64-bit IEEE 754)	Smallest positive non-zero: 4.9e-324, Largest positive non-zero: 1.797693157e308
char	A single character	All Unicode characters

Declaring Variables

In a nutshell, declaring a variable has this syntax:

 [variable type] [identifier]

This works for both reference variables and primitive variables. [variable type] is the type of variable, like int or char. [identifier] is the name for the variable you wish to create, for example, password or number_of_fish. If you wanted to create a int variable called age, you would type this:

int age

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