3Sum Closest

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

    For example, given array S = {-1 2 1 -4}, and target = 1.

    The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

public class Solution {
    public int threeSumClosest(int[] num, int target) {
        if(num == null || num.length < 3) return 0;
        int min = Integer.MAX_VALUE, len = num.length;
        Arrays.sort(num);
        for(int i = 0; i < len - 2; i ++){
            int goal = target - num[i];
            int j = i + 1, k = len - 1;
            while(j < k){
                min = Math.abs(min) < Math.abs(target - num[i] - num[j] - num[k]) ? min : (target - num[i] - num[j] - num[k]);
                if(num[j] + num[k] < goal) j ++;
                else if(num[j] + num[k] > goal) k --;
                else return target;
            }
        }
        return target - min;
    }
}