Java Reference
In-Depth Information
both changes the value of
number
to
3
and evaluates to the value
3
. This allows you to
chain assignment statements. The following changes the values of both the variables,
number1
and
number2
, to
3
:
number2 = (number1 = 3);
The assignment operator automatically is executed right to left if there are no
parentheses, so this is normally written in the following equivalent way:
number2 = number1 = 3;
TIP: Initialize Variables
A variable that has been declared but that has not yet been given a value by some
means, such as an assignment statement, is said to be
uninitialized
. In some instances,
an uninitialized variable may be given some default value, but this is not true in all
cases. Moreover, it makes your program clearer to explicitly give the variable a value,
even if you are simply reassigning it the default value. (The exact details on default
values have been known to change and should not be counted on.)
2
One easy way to ensure that you do not have an uninitialized variable is to initialize
it within the declaration. Simply combine the declaration and an assignment state-
ment, as in the following examples:
uninitialized
variable
int
count = 0;
double
speed = 65.5;
char
grade = 'A';
int
initialCount = 50, finalCount;
Note that you can initialize some variables and not initialize others in a declaration.
Sometimes the compiler may say that you have failed to initialize a variable. In most
cases, this will indeed have occurred. Occasionally, the compiler is mistaken. However,
the compiler will not compile your program until you convince it that the variable in
question is initialized. To make the compiler happy, initialize the variable when it is
declared, even if the variable will be given a different value before the variable is used
for anything. In such cases, you cannot argue with the compiler.
■
2
The official rules are that the variables we are now using, which we will later call
local variables
, are
not automatically initialized. Later in this topic, we will introduce variables called
static variables
and
instance variables
, which are automatically initialized. However, we urge you to never rely on automatic
initialization.
