Section 2.1 Primitive Data Types
The foundation of any program is its data, which is created, manipulated, and stored using a computer. Unlike the numbers that we might write on paper in a mathematics class, when using a computer we must also consider the type of numeric values because each must be stored in the computer’s memory, and each has a different memory size requirement. It will be no surprise that the amount of memory used to store a particular type will increase with the range of values desired as well as how they are encoded. For this reason Java offers multiple numeric primitive types which you may choose to match the anticipated range of values required by your computation.
Following is a table of the eight Java primitive types. Study the table carefully. Notice how as value ranges of each type increases with the number of bytes required (see Description column).
| Type | Size (bytes) | Description |
|---|---|---|
byte |
1 | small integers from -128 to 127 |
short |
2 | integers from -32,768 to 32,767 |
int |
4 | integers from -2,147,483,648 to 2,147,483,647 |
long |
8 | larger integers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 |
float |
4 | floating-point numbers with decimal places and 6 to 7 signficiant digits |
double |
8 | larger floating-point numbers with double precision, 15 to 16 significant digits |
char |
2 | single characters such as ’A’, ’b’, ’5’ or ’!’ |
boolean |
1 | one of two boolean values, true or false. |
We’ll consider each of these types in more detail.
