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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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