Java Reference
In-Depth Information
public double area()
that compute the circumference and area of a polygon. To compute the
perimeter, compute the distance between adjacent points, and total up the
distances. The area of a polygon with corners (x
0
, y
0
),ș, (x
nɨ1
, y
nɨ1
) is
1
2
x
0
y
0
(
+
x
1
y
2
+ւ +
x
n ɨ1
y
0
ɨ
y
0
x
1
ɨ
y
1
x
2
ɨւ ɨ
y
n ɨ1
x
0
)
As test cases, compute the perimeter and area of a rectangle and of a
regular hexagon. Note: You need not draw the polygonȌthat is done in
Exercise P7.15.
Exercise P7.8. Write a program that reads a sequence of integers into an
array and that computes the alternating sum of all elements in the array. For
example, if the program is executed with the input data
1 4 9 16 9 7 4 9 11
then it computes
1 ɨ4 +9 ɨ16 +9 ɨ7 +4 ɨ9 +11 = ɨ2
328
329
PROGRAMMING EXERCISES
Exercise P7.9. Write a program that produces random permutations of the
numbers 1 to 10. To generate a random permutation, you need to fill an
array with the numbers 1 to 10 so that no two entries of the array have the
same contents. You could do it by brute force, by calling
Random.nextInt
until it produces a value that is not yet in the array.
Instead, you should implement a smart method. Make a second array and
fill it with the numbers 1 to 10. Then pick one of those at random, remove
it, and append it to the permutation array. Repeat 10 times. Implement a
class
Permutation Generator
with a method
int[] nextPermutation
