The JavaTM Tutorial

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Trail: Learning the Java Language
Lesson: Language Basics

## Summary of Variables

> When you declare a variable, you explicitly set the variable's name and data type. The Java programming language has two categories of data types: primitive and reference. A variable of primitive type contains a value. This table shows all of the primitive data types along with their sizes and formats:

> Keyword | Description | Size/Format
> (integers)
> `byte` | Byte-length integer | 8-bit two's complement
> `short` | Short integer | 16-bit two's complement
> `int` | Integer | 32-bit two's complement
> `long` | Long integer | 64-bit two's complement
> (real numbers)
> `float` | Single-precision floating point | 32-bit IEEE 754
> `double` | Double-precision floating point | 64-bit IEEE 754
> (other types)
> `char` | A single character | 16-bit Unicode character
> `boolean` | A boolean value (`true` or `false`) | true or false

> The location of a variable declaration implicitly sets the variable's scope, which determines what section of code may refer to the variable by its simple name. There are four categories of scope: member variable scope, local variable scope, parameter scope, and exception-handler parameter scope.

> You can provide an initial value for a variable within its declaration by using the assignment operator (=).

> You can declare a variable as final. The value of a final variable cannot change after it's been initialized.

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