- byte: The
byte data type is an 8-bit signed two's complement integer. It has a minimum
value of -128 and a maximum value of 127 (inclusive). The byte data type can be useful for saving memory
in large
arrays, where the memory savings actually matters. They can also be used in place of
int where their limits help to clarify your code; the fact that a variable's range is limited can
serve as a form of documentation.
- short: The
short data type is a 16-bit signed two's complement integer. It has a
minimum value of -32,768 and a maximum value of 32,767 (inclusive). As with byte, the same guidelines apply:
you can use a short to save memory in large arrays, in situations where the memory savings actually matters.
- int: The
int data type is a 32-bit signed two's complement integer. It has a minimum value of
-2,147,483,648 and a maximum value of 2,147,483,647 (inclusive). For integral values, this data type is generally
the default choice unless there is a reason (like the above) to choose something else. This data type will most likely
be large enough for the numbers your program will use, but if you need a wider range of values, use long
instead.
- long: The
long data type is a 64-bit signed two's complement integer. It has a minimum value of
-9,223,372,036,854,775,808 and a maximum value of 9,223,372,036,854,775,807 (inclusive). Use this data type when you need a
range of values wider than those provided by int.
- float: The
float data type is a single-precision 32-bit IEEE 754 floating point.
Its range of values is beyond the scope of this discussion, but is specified in section
4.2.3
of the Java Language Specification. As with the recommendations for byte and short, use a float (instead of double) if you need to save memory in large arrays
of floating point numbers. This data type should never be used for precise values, such as currency. For that, you will need to
use the
java.math.BigDecimal
class instead.
Numbers and Strings
covers BigDecimal and
other useful classes provided by the Java platform.
- double: The
double data type is a double-precision 64-bit IEEE 754 floating point.
Its range of values is beyond the scope of this discussion, but is specified in section
4.2.3
of the Java Language Specification. For decimal values, this data type is
generally the default choice. As mentioned above, this data type should never be used for precise values, such as currency.
- boolean: The
boolean data type has only two possible values: true and
false. Use this data type for simple flags that track
true/false conditions. This data type represents one bit of
information, but its "size" isn't
something that's precisely defined.
- char: The
char data type is a single 16-bit Unicode character. It has a minimum value of
'\u0000' (or 0) and a maximum value of '\uffff' (or 65,535 inclusive).
| Data Type |
Default Value (for fields) |
| byte |
0 |
| short |
0 |
| int |
0 |
| long |
0L |
| float |
0.0f |
| double |
0.0d |
| char |
'\u0000' |
| String (or any object) |
null |
| boolean |
false |
[링크 : http://java.sun.com/docs/books/tutorial/java/nutsandbolts/datatypes.html ]
|
