Java Reference
In-Depth Information
For example, in Fig. 6.10, the compiler might (internally) use the logical name
“
square
of
int
” for the
square
method that specifies an
int
parameter and “
square
of
double
” for the
square
method that specifies a
double
parameter (the actual names the
compiler uses are messier). If
method1
's declaration begins as
void
method1(
int
a,
float
b)
then the compiler might use the logical name “
method1
of
int
and
float
.” If the param-
eters are specified as
void
method1(
float
a,
int
b)
then the compiler might use the logical name “
method1
of
float
and
int
.” The
order
of
the parameter types is important—the compiler considers the preceding two
method1
headers to be
distinct
.
Return Types of Overloaded Methods
In discussing the logical names of methods used by the compiler, we did not mention the
return types of the methods.
Method calls cannot be distinguished only by return type
. If you
had overloaded methods that differed
only
by their return types and you called one of the
methods in a standalone statement as in:
square(
2
);
the compiler would
not
be able to determine the version of the method to call, because the
return value is
ignored
. When two methods have the
same
signature and
different
return
types, the compiler issues an error message indicating that the method is already defined in
the class. Overloaded methods
can
have
different
return types if the methods have
different
parameter lists. Also, overloaded methods need
not
have the same number of parameters.
Common Programming Error 6.8
Declaring overloaded methods with identical parameter lists is a compilation error re-
gardless of whether the return types are different.
and Filled Shapes
Although you can create many interesting designs with just lines and basic shapes, class
Graphics
provides many more capabilities. The next two features we introduce are colors
and filled shapes. Adding color enriches the drawings a user sees on the computer screen.
Shapes can be filled with solid colors.
Colors displayed on computer screens are defined by their
red
,
green
, and
blue
com-
ponents (called
RGB values
) that have integer values from 0 to 255. The higher the value
of a component color, the richer that color's shade will be. Java uses class
Color
(package
java.awt
) to represent colors using their RGB values. For convenience, class
Color
con-
tains various predefined
static
Color
objects—
BLACK
,
BLUE
,
CYAN
,
DARK_GRAY
,
GRAY
,
GREEN
,
LIGHT_GRAY
,
MAGENTA
,
ORANGE
,
PINK
,
RED
,
WHITE
and
YELLOW
. Each can be accessed
via the class name and a dot (
.
) as in
Color.RED
. You can create custom colors by passing
the red-, green- and blue-component values to class
Color
's constructor:
public
Color(
int
r,
int
g,
int
b)
