Java Reference
In-Depth Information
What value will
myVar
contain? Well, because the ++ is postfixed (it's after the
myNumber
variable),
it will be incremented afterward. So the equation reads: Multiply
myNumber
by 10 plus 1 and then
increment
myNumber
by one.
myVar
=
1 * 10
+
1
=
11
Then add 1 to
myNumber
to get 12, but do this after the value 11 has been assigned to
myVar
. Now
take a look at the following code:
myNumber
=
1;
myVar
=
++
myNumber * 10
+
1;
This time
myNumber
is incremented by one first, then times 10 and plus 1:
myVar
=
2 * 10
+
1
=
21
As you can imagine, such subtlety can easily be overlooked and lead to bugs in code; therefore, it's
usually best to avoid this syntax.
Before going on, this seems to be a good place to introduce another operator: +=. You can
use this operator as a shortcut for increasing the value held by a variable by a set amount. For
example,
myVar
+=
6;
does exactly the same thing as:
myVar
=
myVar
+
6;
You can also do the same thing for subtraction and multiplication, as shown here:
myVar
−=
6;
myVar *
=
6;
which is equivalent to:
myVar
=
myVar - 6;
myVar
=
myVar * 6;
operator precedence
You've seen that symbols that perform some function—like +, which adds two numbers, and
−
,
which subtracts one number from another—are called operators. Unlike people, not all operators
are created equal; some have a higher
precedence
—that is, they get dealt with sooner. A quick look
at a simple example will help demonstrate this point:
var myVariable;
myVariable
=
1
+
1 * 2;
alert(myVariable);
