Practice problems from today

Practice.java

import java.util.ArrayList;

public class Practice
{
	public static void main(String[] args) {
		// An example list of words to test against.
		ArrayList<String> words = new ArrayList<String>(10);
		words.add("foo");
		words.add("bar");
		words.add("baz");
		words.add("slinky");
		words.add("dinky");
		words.add("blinky");
		words.add("bleh");
		words.add("meh");
		words.add("heh");
		words.add("he");

		removeShortestWord(words);
		System.out.println(words);

		System.out.println(calculateAverageLength(words));

		System.out.println(isEveryWordTheSame(words));

		swapFirstAndLast(words);
		System.out.println(words);

		swapIAndJ(words, 3, 5);
		System.out.println(words);
	}

	/* Removes the shortest word in the given list.
	 *
	 * @param words - the ArrayList of words
	 */
	public static void removeShortestWord(ArrayList<String> words) {
		String shortestWord = words.get(0);
		int indexOfShortestWord = 0;
		for (int i = 1; i < words.size(); i++) {
			if (words.get(i).length() < shortestWord.length()) {
				shortestWord = words.get(i);
				indexOfShortestWord = i;
			}
		}
		words.remove(indexOfShortestWord);
	}

	/* Calculates the average word length in the given list of
	 * words.
	 *
	 * @param words - the ArrayList of words
	 */
	public static int calculateAverageLength(ArrayList<String> words) {
		int sumOfLengths = 0;
		for (int i = 0; i < words.size(); i++) {
			sumOfLengths += words.get(i).length();
		}
		return sumOfLengths / words.size();

		// Alternative solution. Using a for-each loop. Remember, it's
		// okay to do this because we're not (1) removing anything
		// from words, (2) adding anything to words, or (3) changing
		// anything inside words. Basically we're not modifying words,
		// and as long as you're not modifying words you can use the
		// for-each syntax.
		/*
		int sumOfLengths = 0;
		for (String word : words) {
			sumOfLengths += word.length();
		}
		return sumOfLengths / words.size();
		*/
	}

	/* Returns true if every word in the given list is the same.
	 * Returns false otherwise.
	 *
	 * @param words - the ArrayList of words
	 */
	public static boolean isEveryWordTheSame(ArrayList<String> words) {
		String firstWord = words.get(0);
		for (int i = 0; i < words.size(); i++) {
			if (!words.get(i).equals(firstWord)) {
				return false;
			}
		}
		return true;

		// Alternative solution. Again, since we're not modifying
		// words, we can use the for-each loop. We're only reading
		// stuff from words.
		/*
		String firstWord = words.get(0);
		for (String word : words) {
			if (!word.equals(firstWord)) {
				return false;
			}
		}
		return true;
		*/
	}

	/* Swaps the first and last words in the given list. You can
	 * assume there are at least two elements.
	 *
	 * @param words - the ArrayList of words
	 */
	public static void swapFirstAndLast(ArrayList<String> words) {
		String firstWord = words.get(0);
		String lastWord = words.get(words.size() - 1);
		words.set(0, lastWord);
		words.set(words.size() - 1, firstWord);

		// Alternative solution: using the method you wrote below.
		// swapIAndJ(words, 0, words.size() - 1);
	}

	/* Swaps the two words at index i and index j. You can assume
	 * i and j are valid indices (they won't be longer than the array
	 * or less than 0).
	 *
	 * @param words - the ArrayList of words
	 */
	public static void swapIAndJ(ArrayList<String> words, int i, int j) {
		String firstWord = words.get(i);
		String secondWord = words.get(j);
		words.set(i, secondWord);
		words.set(j, firstWord);
	}
}