collections-programming-answers.md

CSE 143

Collections Programming Answers

Final Study Session

1. extractEqual. Two possible solutions are shown below.

   public Set<Point> extractEqual(Set<Point> data) {
   	Set<Point> result = new HashSet<Point>();
   	for (Point p : data)
   		if (p.getX() == p.getY())
   			result.add(p);
   	return result;
   }

   public Set<Point> extractEqual(Set<Point> data) {
   	Set<Point> result = new HashSet<Point>();
   	Iterator<Point> i = data.iterator();
   	while (i.hasNext()) {
   		Point p = i.next();
   		if (p.getX() == p.getY())
   			result.add(p);
   	}
   	return result;
   }

2. convert. One possible solution appears below.

   public static Map<Integer, Integer> convert(int[] list) {
   	Map<Integer, Integer> result = new TreeMap<Integer, Integer>();
   	for (int i = 0; i < list.length; i++) {
   		if (list[i] != 0) {
   			result.put(i, list[i]);
   		}
   	}
   	return result;
   }