test2

Class Utility2A

java.lang.Object

test2.Utility2A

public class Utility2A
extends Object

Method Summary

Modifier and Type	Method and Description
static int	alternatingSum(List<Integer> t) Computes the alternating sum of the integers in the argument list.
static Integer	last(List<Integer> t) Returns the last integer in the argument list.
static int	totalArea(List<Integer> widths, List<Integer> heights) Computes the sum of the areas of zero or more rectangles.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

last

public static Integer last(List<Integer> t)

Returns the last integer in the argument list.

Parameters:

t - a list of integers

Returns:

the last integer in t

Preconditions:

t is not empty

totalArea

public static int totalArea(List<Integer> widths,
                            List<Integer> heights)

Computes the sum of the areas of zero or more rectangles. The width of each rectangle is given by the list widths. The height of each rectangle is given by the list heights. For example, consider the two lists:

 widths   [1, 5, 10]
 heights  [2, 3,  4]
 

The sum of the areas is equal to (1 * 2 + 5 * 3 + 10 * 4). If a width or height of a rectangle is less than zero then that area is not included in the sum.

Parameters:

widths - a non-null list of rectangle widths

heights - a non-null list of rectangle heights

Returns:

the sum of the rectangle areas not including negative areas

Throws:

IllegalArgumentException - if widths and heights are lists of different sizes

alternatingSum

public static int alternatingSum(List<Integer> t)

Computes the alternating sum of the integers in the argument list. In an alternating sum, every second element is negated before adding it to the sum. For example, consider the list:

 [0, 1, 2, 3, 4, 5]
 

The alternating sum is given by (0 - 1 + 2 - 3 + 4 - 5). The alternating sum for an empty list is zero.

Parameters:

t - a non-null list of integers

Returns:

the alternating sum of the integers in t