Java Reference
In-Depth Information
2.25
(Odd or Even)
Write an application that reads an integer and determines and prints wheth-
er it's odd or even. [
Hint:
Use the remainder operator. An even number is a multiple of 2. Any mul-
tiple of 2 leaves a remainder of 0 when divided by 2.]
2.26
(Multiples)
Write an application that reads two integers, determines whether the first is a
multiple of the second and prints the result. [
Hint:
Use the remainder operator.]
2.27
(Checkerboard Pattern of Asterisks)
Write an application that displays a checkerboard pat-
tern, as follows:
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
2.28
(Diameter, Circumference and Area of a Circle)
Here's a peek ahead. In this chapter, you
learned about integers and the type
int
. Java can also represent floating-point numbers that contain
decimal points, such as 3.14159. Write an application that inputs from the user the radius of a circle
as an integer and prints the circle's diameter, circumference and area using the floating-point value
3.14159 for
π
. Use the techniques shown in Fig. 2.7. [
Note:
You may also use the predefined con-
stant
Math.PI
for the value of
π
. This constant is more precise than the value 3.14159. Class
Math
is defined in package
java.lang
. Classes in that package are imported automatically, so you do not
need to
import
class
Math
to use it.] Use the following formulas (
r
is the radius):
diameter
= 2
r
circumference
= 2
π
r
π
r
2
Do not store the results of each calculation in a variable. Rather, specify each calculation as the
value that will be output in a
System.out.printf
statement. The values produced by the circum-
ference and area calculations are floating-point numbers. Such values can be output with the for-
mat specifier
%f
in a
System.out.printf
statement. You'll learn more about floating-point
numbers in Chapter 3.
2.29
(Integer Value of a Character)
Here's another peek ahead. In this chapter, you learned about
integers and the type
int
. Java can also represent uppercase letters, lowercase letters and a consider-
able variety of special symbols. Every character has a corresponding integer representation. The set
of characters a computer uses together with the corresponding integer representations for those
characters is called that computer's character set. You can indicate a character value in a program
simply by enclosing that character in single quotes, as in
'A'
.
You can determine a character's integer equivalent by preceding that character with
(int)
, as in
(
int
)
'A'
An operator of this form is called a cast operator. (You'll learn about cast operators in Chapter 4.)
The following statement outputs a character and its integer equivalent:
System.out.printf(
"The character %c has the value %d%n"
,
'A'
, ((
int
)
'A'
));
When the preceding statement executes, it displays the character
A
and the value
65
(from the Uni-
code
®
character set) as part of the string. The format specifier
%c
is a placeholder for a character (in
this case, the character
'A'
).
Using statements similar to the one shown earlier in this exercise, write an application that dis-
plays the integer equivalents of some uppercase letters, lowercase letters, digits and special symbols.
Display the integer equivalents of the following:
A B C a b c 0 1 2 $ * + /
and the blank character.
area
=