Java Reference
In-Depth Information
ing executed. If you don't do this, once you call the method, it will never return. This type
of error is very common when working with recursion. Use
println( )
statements liberally
so that you can watch what is going on and abort execution if you see that you have made
a mistake.
Understanding static
There will be times when you will want to define a class member that will be used inde-
pendently of any object of that class. Normally a class member must be accessed through
an object of its class, but it is possible to create a member that can be used by itself, without
reference to a specific instance. To create such a member, precede its declaration with the
keyword
static
. When a member is declared
static
, it can be accessed before any objects of
its class are created, and without reference to any object. You can declare both methods and
variables to be
static
. The most common example of a
static
member is
main( )
.
main( )
is declared as
static
because it must be called by the JVM when your program begins. Out-
side the class, to use a
static
member, you need only specify the name of its class followed
by the dot operator. No object needs to be created. For example, if you want to assign the
value 10 to a
static
variable called
count
that is part of the
Timer
class, use this line:
This format is similar to that used to access normal instance variables through an object,
except that the class name is used. A
static
method can be called in the same way—by use
of the dot operator on the name of the class.
Variables declared as
static
are, essentially, global variables. When an object is declared,
no copy of a
static
variable is made. Instead, all instances of the class share the same
static
variable. Here is an example that shows the differences between a
static
variable and an
instance variable:
