Java Reference
In-Depth Information
10.
You can get the length of a string by invoking its
length()
method, retrieve a char-
acter at the specified index in the string using the
charAt(index)
method, and
use the
indexOf
and
lastIndexOf
methods to find a character or a substring in
a string.
11.
You can use the
concat
method to concatenate two strings, or the plus (
+
) operator to
concatenate two or more strings.
12.
You can use the
substring
method to obtain a substring from the string.
13.
You can use the
equals
and
compareTo
methods to compare strings. The
equals
method returns
true
if two strings are equal, and
false
if they are not equal. The
compareTo
method returns
0
, a positive integer, or a negative integer, depending on
whether one string is equal to, greater than, or less than the other string.
14.
The
printf
method can be used to display a formatted output using format
specifiers.
Q
UIZ
P
ROGRAMMING
E
XERCISES
Section 4.2
4.1
(
Geometry: area of a pentagon
) Write a program that prompts the user to enter
the length from the center of a pentagon to a vertex and computes the area of the
pentagon, as shown in the following figure.
r
s
2
5
*
The formula for computing the area of a pentagon is
Area
=
≤
, where
5
4
*
tan
¢
2
r
sin
5
,
s
is the length of a side. The side can be computed using the formula
s
=
where
r
is the length from the center of a pentagon to a vertex. Round up two digits
after the decimal point. Here is a sample run:
Enter the length from the center to a vertex: 5.5
The area of the pentagon is 71.92
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