A variable
is a named memory location which temporarily stores data that
can change while the program is running.
A final
is a named memory location which temporarily stores data that
remains the same throughout the execution of the program.
It is a constant variable in the program.
The type
of a variable indicates what kind of value it will
store.
The name of a variable is known as its
identifier.
A variable is given a value through an
assignment statement.
Java recognizes different data types of
variables depending upon what kind of data they can contain.
Java has eight built-in primitive data types designated by reserved
words:
byte
short
int
long |
float
double
char
boolean |
Variables of different types occupy different amounts of
memory space and are described as having different sizes.
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Of the eight primitive data types in Java, the four most commonly used are:
double, int, boolean, and
char . When you learn about objects, you will discuss
the differences between primitives and objects.
Variables Most Often Used
|
Data Type |
Java Keyword |
Kind of Value |
Bytes of Memory |
Range of Values |
| Character |
char |
1 character -
Unicode |
2 |
not
applicable |
| Byte |
byte |
integer |
1 |
-128 to127
|
| Short integer |
short |
Integers |
2 |
-32,768 to
32,767
(-215 to 215 - 1)
|
| Integer |
int |
Integers |
4 |
-2,147,483,648 to 2,147,483,647
(-231 to 231 - 1) |
| Long Integer |
long |
Integers |
8 |
-9223372036854775808 to
9223372036854775807
(-263 to 263 - 1) |
| Float |
float |
Decimal
values to 7 decimal digit precision |
4 |
3.4e-38 to
3.4e38
positive and negative
|
| Double |
double |
Decimal
values to 15 decimal digit precision |
8 |
1.7e-308 to
1.73e308
positive and negative
|
| Boolean |
bool |
Boolean
(Logical) values
True or False |
1 |
not
applicable |
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Rules for assigning
variables:
Assign short,
int or
long data types when you are
sure a variable is a whole number (NO decimal points). Which
type you choose depends upon the size of the numbers.
Assign float or
double when decimals are
needed. Which type you choose depends upon the size of the
numbers.
Assign char if the
variable will always contain only ONE character of data.
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