Write a function, that given a list (or array) of integers and an integer s, prints all combinations of 2 numbers in the list that sum to s.

CombinationSearch.java

/*
 Write a function, that given a list (or array) of integers and an integer s,
 prints all combinations of 2 numbers in the list that sum to s.
*/


import java.util.*;

public class CombinationSearch {

    static Random r = new Random();

    static int printCombinations(List<Integer> list, Integer value) {
        if (list.size() == 0) {
            return 0;
        }

        Collections.sort(list);

        Integer[] array = new Integer[list.size()];
        array = list.toArray(array);
        int count = 0;
        for (int i = 0; i < list.size(); i++) {
            int current = array[i];
            int foundKey = Arrays.binarySearch(array, 0, list.size(), value - current);
            if (foundKey >= 0) {
                System.out.printf("Found:\t%d\t%d\n", current, array[foundKey]);
                count++;
            } else {
                if (current > value) break;
            }
        }
        return count;
    }

    static int printCombinationsSlow(List<Integer> list, Integer value) {
        if (list.size() == 0) {
            return 0;
        }

        Collections.sort(list);

        int count = 0;
        for (Integer i : list) {
            for (Integer j : list) {
                if (i + j == value) {
                    System.out.printf("Found:\t%d\t%d\n", i, j);
                    count++;
                } else {
                    if (i + j > value) break;
                }
            }
        }
        return count;
    }

    private static List<Integer> createRandomList(int length, int bound) {
        List<Integer> randomList = new ArrayList<>(length);
        for (int i = 0; i < length; i++) {
            randomList.add(r.nextInt(bound));
        }
        return randomList;
    }

    public static void main(String[] args) {
        long start = System.currentTimeMillis();
        int length = Integer.valueOf((args.length > 0) ? args[0] : "99");
        int value = Integer.valueOf((args.length > 1) ? args[1] : "50");
        int algo = Integer.valueOf((args.length > 2) ? args[2] : "0");
        List<Integer> list = createRandomList(length, length * 2);
        System.out.printf("Looking in a list with length %d for sums adding to %d ", length, value);

        int count=0;
        String method;
        if (algo > 0) {
            count = printCombinationsSlow(list, value);
            method = "printCombinationsSlow";
        } else {
            count = printCombinations(list, value);
            method = "printCombinations";
        }


        long end = System.currentTimeMillis();
        System.out.printf("\n\nThis took %d ms for %d matches using %s algorithm", end - start, count, method);
    }
}