Solutions to ArrayList practice questions

Solutions.java

import java.util.ArrayList;

public class Solutions
{
	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");

		// Test solutions to questions below.
		System.out.println("Sup? Good luck on your exam. Hope these practice questions help. :)");
		System.out.println("Given the list of words: foo bar baz slinky dinky blinky bleh meh heh");

		// Test removeEveryOther.
		ArrayList<String> result = new ArrayList<String>(words);
		removeEveryOther(result);
		System.out.println(
			"\nRemoving every other word should give you: [foo, baz, dinky, bleh, heh]\n"
			+ "Your answer is: " + result
		);
		assert result.toString().equals("[foo, baz, dinky, bleh, heh]");

		// Test removeEh.
		result = new ArrayList<String>(words);
		removeEh(result);
		System.out.println(
			"\nRemoving words that end with \"eh\" give you: [foo, bar, baz, slinky, dinky, blinky]\n"
			+ "Your answer is: " + result
		);
		assert result.toString().equals("[foo, bar, baz, slinky, dinky, blinky]");

		// Test removeWordsWithSuffix.
		result = new ArrayList<String>(words);
		removeWordsWithSuffix(result, "linky");
		System.out.println(
			"\nRemoving words that end with \"linky\" give you: [foo, bar, baz, dinky, bleh, meh, heh]\n"
			+ "Your answer is: " + result
		);
		assert result.toString().equals("[foo, bar, baz, dinky, bleh, meh, heh]");

		// Test removeInky.
		result = new ArrayList<String>(words);
		removeInky(result);
		System.out.println(
			"\nRemoving words that end with \"inky\" should give you: [foo, bar, baz, bleh, meh, heh]\n"
			+ "Your answer is: " + result
		);
		assert result.toString().equals("[foo, bar, baz, bleh, meh, heh]");

		// Test shortestString.
		result = new ArrayList<String>(words);
		String shortestString = shortest(result);
		System.out.println(
			"\nThe shortest string should be \"heh\" (if you break ties by taking the one closest to the end).\n"
			+ "Your answer is: " + shortestString
		);
		assert shortestString.equals("heh");

		// Test toCaps.
		result = new ArrayList<String>(words);
		toCaps(result);
		System.out.println(
			"\nIf you convert everything to caps you should have: [FOO, BAR, BAZ, SLINKY, DINKY, BLINKY, BLEH, MEH, HEH]\n"
			+ "Your answer is: " + result
		);
		assert result.toString().equals("[FOO, BAR, BAZ, SLINKY, DINKY, BLINKY, BLEH, MEH, HEH]");
	}

	/* Removes every other word from the given list
	 * of words. For example, if the input consists of
	 * 10 words, remove the second, fourth, sixth, eigth,
	 * and tenth words.
	 *
	 * @param words - an ArrayList of Strings
	 */
	public static void removeEveryOther(ArrayList<String> words) {
		for (int i = 1; i < words.size(); i += 2) {
			words.remove(i);
			i--;
		}

		// Alternate solution no. 1 (taking advantage of the fact that an index is skipped)
		/*
		for (int i = 1; i < words.size(); i++) {
			words.remove(i);
		}
		*/
	}

	/* Removes every word that ends with the suffix "eh". 
	 * 
	 * @param words - an ArrayList of Strings
	 */
	public static void removeEh(ArrayList<String> words) {
		for (int i = 1; i < words.size(); i++) {
			if (words.get(i).length() < 2) {
				continue;
			}
			int indexOfSecondToLastCharacter = words.get(i).length() - 2;
			String substringFromLastTwoCharacters = words.get(i).substring(indexOfSecondToLastCharacter);
			if (substringFromLastTwoCharacters.equals("eh")) {
				words.remove(i);
				i--;
			}
		}

		/*
		// Alternative solution no. 1 (not using variables)
		for (int i = 1; i < words.size(); i++) {
			if (words.get(i).length() < 2) {
				continue;
			}
			if (words.get(i).substring(words.get(i).length() - 2).equals("eh")) {
				words.remove(i);
				i--;
			}
		}
		*/

		/*
		// Alternative solution no. 2 (using the endsWith method - if you know this method exists)
		for (int i = 1; i < words.size(); i++) {
			if (words.get(i).endsWith("eh")) {
				words.remove(i);
				i--;
			}
		}
		*/
	}

	/* Removes every word that ends with the given suffix.
	 * (this is really similar to the previous question). 
	 *
	 * @param words - an ArrayList of Strings
	 * @param suffix - the suffix. Remove words that end with this suffix.
	 */
	public static void removeWordsWithSuffix(ArrayList<String> words, String suffix) {
		for (int i = 1; i < words.size(); i++) {
			if (words.get(i).length() < suffix.length()) {
				continue;
			}
			int indexOfSuffixStart = words.get(i).length() - suffix.length();
			String suffixOfCurrentWord = words.get(i).substring(indexOfSuffixStart);
			if (suffixOfCurrentWord.equals(suffix)) {
				words.remove(i);
				i--;
			}
		}

		/*
		// Alternative solution no. 1 (not using variables)
		for (int i = 1; i < words.size(); i++) {
			if (words.get(i).length() < suffix.length()) {
				continue;
			}
			if (words.get(i).substring(words.get(i).length() - suffix.length()).equals(suffix)) {
				words.remove(i);
				i--;
			}
		}
		*/

		// Alternative solution no. 2 (using the endsWith method - if you know this method exists)
		/*
		for (int i = 1; i < words.size(); i++) {
			if (words.get(i).endsWith(suffix)) {
				words.remove(i);
				i--;
			}
		}
		*/
	}

	/* Removes every word that ends with the suffix "inky".
	 * How can you use the previous method (removeWordsWithSuffix)
	 * to implement the solution for this one?
	 *
	 * @param words - an ArrayList of Strings
	 */
	public static void removeInky(ArrayList<String> words) {
		removeWordsWithSuffix(words, "inky");
	}

	/* Finds the shortest word (where you compare words by the number
	 * of characters) in the given list of words.
	 *
	 * If there is a tie, then take the one that occurs LATER in the
	 * list.
	 *
	 * @param words - an ArrayList of Strings
	 */
	public static String shortest(ArrayList<String> words) {
		String shortestSoFar = null;
		for (String word : words) {
			if (shortestSoFar == null || word.length() <= shortestSoFar.length()) {
				shortestSoFar = word;
			}
		}
		return shortestSoFar;

		// Alternative solution - using the other kind of for-loop
		/*
		String shortestSoFar = null;
		for (int i = 0; i < words.size(); i++) {
			String word = words.get(i);
			if (shortestSoFar == null || word.length() <= shortestSoFar.length()) {
				shortestSoFar = word;
			}
		}
		return shortestSoFar;
		*/
	}

	/* Converts every word in the given list of words to caps.
	 * You can assume in a word contains only alphabetic characters.
	 *
	 * @param words - an ArrayList of Strings
	 */
	public static void toCaps(ArrayList<String> words) {
		// Alternative solution no .1 (using toUpperCase method - if you know this method exists)
		for (int i = 0; i < words.size(); i++) {
			String currentWord = words.get(i);
			char[] charactersOfCurrentWord = currentWord.toCharArray();
			char[] charactersOfFixedWord = new char[currentWord.length()]; // We'll fill this up.
			for (int j = 0; j < charactersOfCurrentWord.length; j++) {
				charactersOfFixedWord[j] = (char)(charactersOfCurrentWord[j] + ('A' - 'a'));
			}
			String fixedWord = new String(charactersOfFixedWord);
			words.set(i, fixedWord);
		}

		/*
		// Alternative solution no .1 (using toUpperCase method - if you know this method exists)
		for (int i = 0; i < words.size(); i++) {
			words.set(i, words.get(i).toUpperCase());
		}
		*/
	}
}