CSE142 Sample ArrayList Problems handout #28 Recall that the primary methods for manipulating an ArrayList<E> are: add(E value) appends value at end of list add(int index, E value) inserts given value at given index, shifting subsequent values right clear() removes all elements of the list get(int index) returns the value at given index remove(int index) removes and returns value at given index, shifting subsequent values left set(int index, E value) replaces value at given index with given value size() returns the number of elements in list 1. ArrayLists. Write a static method maxLength that takes an ArrayList of Strings as a parameter and that returns the length of the longest String in the list. If your method is passed an empty ArrayList, it should return 0. 2. ArrayLists. Write a static method minToFront that takes an ArrayList of ints as a parameter and that moves the minimum value in the list to the front, otherwise preserving the order of the elements. For example, if a variable called list stores the following values: (3, 8, 92, 4, 2, 17, 9) and you make the following call: minToFront(list); The value 2 is the minimum, so the list should store the following values after the call: (2, 3, 8, 92, 4, 17, 9). 3. ArrayLists. Write a static method removeEvenLength that takes an ArrayList of Strings as a parameter and that removes all of the Strings of even length from the list. 4. ArrayLists. Write a static method stutter that takes an ArrayList of Strings as a parameter and that replaces every String with two of that String. For example, if the list stores the values ("how", "are", "you?") before the method is called, it should store the values ("how", "how", "are", "are", "you?", "you?") after the method finishes executing. 5. ArrayList. Write a static method removeDuplicates that takes as a parameter a sorted ArrayList of Strings and that eliminates any duplicates from the list. For example, suppose that an ArrayList called "list" contains the following values: [be, be, is, not, or, question, that, the, to, to] After calling removeDuplicates(list) the list should store the following values: [be, is, not, or, question, that, the, to] Because the values will be sorted, all of the duplicates will be grouped together. You may assume that the ArrayList contains only String values, but it might be empty. Write your solution to removeDuplicates below.
Solution to Sample ArrayList Problems 1. One possible solution appears below. public static int maxLength(ArrayList<String> list) { int max = 0; for (int i = 0; i < list.size(); i++) { String s = list.get(i); if (s.length() > max) { max = s.length(); } } return max; } 2. One possible solution appears below. public static void minToFront(ArrayList<Integer> list) { int min = 0; for (int i = 1; i < list.size(); i++) { if (list.get(i) < list.get(min)) { min = i; } } list.add(0, list.remove(min)); } 3. One possible solution appears below. public static void removeEvenLength(ArrayList<String> list) { int i = 0; while (i < list.size()) { if (get(i).length() % 2 == 0) { list.remove(i); } else { i++; } } } 4. One possible solution appears below. public static void stutter(ArrayList<String> list) { for (int i = 0; i < list.size(); i += 2) list.add(i, list.get(i)); } 5. One possible solution appears below. public static void removeDuplicates(ArrayList<String> list) { int index = 0; while (index < list.size() - 1) { if (list.get(index).equals(list.get(index + 1))) { list.remove(index + 1); } else { index++; } } }
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Last modified: Tue Dec 6 11:53:39 PST 2005