Java Reference
In-Depth Information
boolean
The
boolean
data type indicates whether something is true or false. In fact, those two words (
true
and
false
) are the only two values
boolean
data types can have.
■
Note
true
and
false
are reserved words in Java. You can't use them for anything other than the value of a
boolean variable. For example, trying to create an
int
called
true
throws an error.
char
The
char
data type holds two 8-bit bytes and is meant to represent characters. It's stored as an unsigned
16-bit integer with a minimum value of 0 and a maximum value of 65,535. However, you should never
use a
char
to store a number, because that can lead to confusion. Use
char
variables to hold individual
characters, and you'll avoid trouble.
So why is the maximum so big when relatively few characters exist? Well, when you look at all the
character sets in use all around the world, 65,535 isn't so unreasonable. In fact, it's not enough when
dealing with traditional Chinese.
■
Tip
If you're curious about how to handle characters from other languages, look up Unicode, which is a
standard that defines all the world's characters. For more on handling multi-byte characters, look up variable-
width encoding.
The Special Type: String
String
is a type that has some of the characteristics of both a primitive and an object. Strictly speaking, it
is an object; that is, a
String
class defines it. A
String
object is a sequence of characters (and Java
provides utilities for turning a
String
object into a collection of
char
primitives and for making a
String
object from such a collection). It's often handy to work on the collection (the string) rather than on each
character, so Java (and nearly all other programming languages) provides a
String
object.
Java offers special support for the
String
class that lets
String
objects act a little like primitives. In
particular, you can create a
String
object by using the equals sign (
=
), and you can concatenate
String
objects with the plus sign (
+
), as shown in Listing 3-1. Concatenation applies only to strings, by the way.
If you use a plus symbol with the other data types, you either get an error (try adding two
boolean
values
and you'll see it) or you get the mathematical plus operation that you usually associate with the plus
symbol.
