Iterating through SortedSet in Java

Question

I am trying to create intervals for double values stored in a SortedSet.

Below is my code:

 public class Trail {
    public static void main(String[] args) {
        SortedSet<Double> val = new TreeSet<Double>();
        val.add(1.0);
        val.add(2.0);
        val.add(11.0);
        val.add(12.0);

        ArrayList<String> arr = new ArrayList<String>();
        double posinf = Double.POSITIVE_INFINITY;
        double neginf = Double.NEGATIVE_INFINITY;
        arr.add(neginf+ " - " +val.first());
        Iterator<Double> it = val.iterator();
        while (it.hasNext()) {
            // Get element
            Object lowerBound = it.next();
            Object upperBound = it.next();
            arr.add(lowerBound+" - "+upperBound);
        }
        arr.add(val.last() + " - "+ posinf);
        System.out.println("Range array: "+arr);
    }
 }

My current output is:

Range array: [-Infinity - 1.0, 1.0 - 2.0, 11.0 - 12.0, 12.0 - Infinity]

I expect range array as:

[-Infinity - 1.0, 1.0 - 2.0, 2.0 - 11.0, 11.0 - 12.0, 12.0 - Infinity]

Answer 1

You are consuming two elements in each iteration of your loop (which would have thrown an exception if the number of elements was odd). You should consume just one in each iteration :

    Iterator<Double> it = val.iterator();
    Double lowerBound = neginf;
    while (it.hasNext()) {
        // Get element
        Double upperBound = it.next();
        arr.add(lowerBound+" - "+upperBound);
        lowerBound = upperBound;
    }
    arr.add(lowerBound  + " - "+ posinf);