ArrayList Quiz

Consider the following code segment. ArrayList oldList = new ArrayList(); oldList.add(100); oldList.add(200); oldList.add(300); oldList.add(400); ArrayList newList = new ArrayList(); newList.add(oldList.remove(1)); newList.add(oldList.get(2)); System.out.println(newList); What, if anything, is printed as a result of executing the code segment?

• [100, 300, 400]

• [200, 300]

• [200, 400]

• Nothing is printed because the code segment does not compile.

• Nothing is printed because an IndexOutOfBoundsException will occur.

Consider the following method countNegatives, which searches an ArrayList of Integer objects and returns the number of elements in the list that are less than 0. public static int countNegatives(ArrayList arr) { int count = 0; for (int j = 0; j < arr.size(); j++) // Line 4 { if (arr.get(j) < 0) { count++; } } return count; } Which of the following best explains the impact to the countNegatives method when, in line 4, j < arr.size() is replaced with j <= arr.size() - 1?

• It has no impact on the behavior of the method.

• It causes the method to ignore the last element in arr.

• It causes the method to throw an IndexOutOfBoundsException.

• It reduces the size of arr by 1 and the last element will be removed.

• It changes the number of times the loop executes, but all indexes in arr will still be accessed.

Consider the following method findValue, which takes an ArrayList of String elements and a String value as parameters and returns true if the String value is found in the list and false otherwise. public static boolean findValue(ArrayList arr, String key) { for (int j = 0; j < arr.size(); j++) // Line 3 { if (arr.get(j).equals(key)) { return true; } } return false; } Which of the following best explains the impact to the findValue method when, in line 3, int j = 0 is replaced by int j = 1 ?

• It has no impact on the behavior of the method.

• It will cause the method to return a different result when the key value is not in the list.

• It will cause the method to return a different result when the key value is found only at the first index in the list.

• It will cause the method to return a different result when the key value is found only at the last index in the list.

• It will cause the method to throw an array index out of bounds exception.

Consider the following method, inCommon, which takes two Integer ArrayList parameters. The method returns true if the same integer value appears in both lists at least one time, and false otherwise. public static boolean inCommon(ArrayList a, ArrayList b) { for (int i = 0; i < a.size(); i++) { for (int j = 0; j < b.size(); j++) // Line 5 { if (a.get(i).equals(b.get(j))) { return true; } } } return false; } Which of the following best explains the impact to the inCommon method when line 5 is replaced by for (int j = b.size() - 1; j > 0; j--) ?

• It has no impact on the behavior of the method.

• It will cause the method to return a different result when the common value is not in the list.

• It will cause the method to return a different result when the common value is found only at the first index in the list.

• It will cause the method to return a different result when the common value is found only at the last index in the list.

• It will cause the method to throw an array index out of bounds exception.

What is printed as a result of executing the code segment?

• Alex Alex Alex

• Alex Alex Alex Alex Bob Carl

• Alex Bob Carl Alex Alex Alex

• Alex Bob Carl Alex Bob Carl

• Nothing is printed because the first print statement will cause a runtime exception to be thrown.

In the following code segment, assume that the ArrayList wordList has been initialized to contain the String values ["apple", "banana", "coconut", "lemon", "orange", "pear"]. int count = 0; for (String word : wordList) { if (word.indexOf("a") >= 0) { count++; } } System.out.println(count); What is printed as a result of executing the code segment?

• 1

• 2

• 3

• 4

• 5

Consider the following method, remDups, which is intended to remove duplicate consecutive elements from nums, an ArrayList of integers. For example, if nums contains [1, 2, 2, 3, 4, 3, 5, 6], then after executing remDups(nums), nums should contain [1, 2, 3, 4, 3, 5, 6]. public static void remDups(ArrayList nums) { for (int j = 0; j < nums.size() - 1; j++) { if (nums.get(j).equals(nums.get(j + 1))) { nums.remove(j); j++; } } } The code does not always work as intended. Which of the following lists can be passed to remDups to show that the method does NOT work as intended?

• [1, 1, 2, 3, 3, 4, 5]

• [1, 2, 2, 3, 3, 4, 5]

• [1, 2, 2, 3, 4, 4, 5]

• [1, 2, 2, 3, 4, 5, 5]

• [1, 2, 3, 3, 4, 5, 5]

Consider the following statement, which is intended to create an ArrayList named years that can be used to store elements both of type Integer and of type String. /* missing code */ = new ArrayList(); Which of the following can be used to replace /* missing code */ so that the statement compiles without error?

• ArrayList years

• ArrayList years()

• ArrayList years[]

• ArrayList years

• ArrayList years

In the following code segment, assume that the ArrayList data has been initialized to contain the Integer values [4, 3, 4, 5, 3, 4]. int j = 0; while (j < data.size() - 1) { if (data.get(j) > data.get(j + 1)) { System.out.print(data.get(j + 1) + " "); } j++; } What, if anything, is printed as a result of executing the code segment?

• 3 3

• 4 5

• 4 5 4

• Nothing is printed because the code segment does not compile.

• Nothing is printed because an IndexOutOfBoundsException occurs.

In the code segment below, assume that the ArrayList object numbers has been properly declared and initialized to contain [0, 2, 4, 5]. for (int k = numbers.size() - 1; k >= 0; k--) { if (numbers.get(k) > k) { System.out.print(k + " "); } } What, if anything, is printed as a result of executing the code segment?

• 0

• 2

• 4

• 5

• Nothing is printed