Question

RrayList Mystery Consider the following method:

public static void mystery(ArrayList list) {

for (int i = 1; i < list.size(); i += 2) {

if (list.get(i - 1) >= list.get(i)) {

list.remove(i);

list.add(0, 0);

}

}

System.out.println(list);

} Write the output produced by the method when passed each of the following ArrayLists: List Output

a) [10, 20, 10, 5]

b) [8, 2, 9, 7, -1, 55]

c) [0, 16, 9, 1, 64, 25, 25, 14

Answer 1

a)

int: [10, 20, 10, 5]

out: [0, 10, 20, 10]

b)

int: [8, 2, 9, 7, -1, 55]

out: [0, 0, 8, 9, -1, 55]

c)

int: [0, 16, 9, 1, 64, 25, 25, 14]

out: [0, 0, 0, 0, 16, 9, 64, 25]

Step-by-step explanation:

What the code is doing is changing the list if and only if the item number i, where i is an odd position on the list, is greater than the item number i-1. If the condition mentioned is satisfied, the element number i is removed, and a zero is added to the beginning of the list; this is why the dimension of the input is equal to the output (for every element removed a zero is added).

Note:

• The first item of a list is the item 0
• .add method can receive two parameters the first indicating the position where the element will be added and the second the element to be added.
• .get method allows you to select any element on the list by its index.
• .size method gives you the size of the list
• In the for loop i += 2 indicates an increment of two, since we start with i = 1 we are going to iterate through odd numbers i = 1,3,5,7...