Java Reference
In-Depth Information
constructor when you create a
BigDecimal
. You may also provide a
MathContext
to var-
ious
BigDecimal
methods that perform calculations. Class
MathContext
contains several
pre-configured
MathContext
objects that you can learn about at
By default, each pre-configured
MathContext
uses so called “bankers rounding” as ex-
plained for the
RoundingMode
constant
HALF_EVEN
at:
Scaling
BigDecimal
Values
A
BigDecimal
's scale is the number of digits to the right of its decimal point. If you need
a
BigDecimal
rounded to a specific digit, you can call
BigDecimal
method
setScale
. For
example, the following expression returns a
BigDecimal
with two digits to the right of the
decimal point and using bankers rounding:
amount.setScale(
2
,
RoundingMode.HALF_EVEN
)
Objects with Graphics
Most of the graphics you've seen to this point did not vary with each program execution.
Exercise 6.2 in Section 6.13 asked you to create a program that generated shapes and col-
ors at random. In that exercise, the drawing changed every time the system called
paint-
Component
. To create a more consistent drawing that remains the same each time it's
drawn, we must store information about the displayed shapes so that we can reproduce
them each time the system calls
paintComponent
. To do this, we'll create a set of shape
classes that store information about each shape. We'll make these classes “smart” by allow-
ing objects of these classes to draw themselves by using a
Graphics
object.
Class
MyLine
Figure 8.17 declares class
MyLine
, which has all these capabilities. Class
MyLine
imports
classes
Color
and
Graphics
(lines 3-4). Lines 8-11 declare instance variables for the co-
ordinates of the endpoints needed to draw a line, and line 12 declares the instance variable
that stores the color of the line. The constructor at lines 15-22 takes five parameters, one
for each instance variable that it initializes. Method
draw
at lines 25-29 requires a
Graph-
ics
object and uses it to draw the line in the proper color and between the endpoints.
1
// Fig. 8.17: MyLine.java
2
// MyLine class represents a line.
3
import
java.awt.Color;
4
import
java.awt.Graphics;
5
6
public
class
MyLine
7
{
Fig. 8.17
|
MyLine
class represents a line. (Part 1 of 2.)
