这个题很简单，还是取一个值，然后另外两个值从两端向中间逼近

public class Solution {    public int threeSumClosest(int[] nums, int target) {        int length = nums.length;        List
    
      numList = new ArrayList
     
      (length);        for (int num : nums) {            numList.add(num);        }        Collections.sort(numList);        int sum1 = numList.get(0) + numList.get(1) + numList.get(2);        int sum2 = numList.get(length-1) + numList.get(length-2) + numList.get(length-3);        int max1 = distance(sum1, target);        int max2 = distance(sum2, target);        int max = max1 < max2? max1:max2;        int targetSum = max1 < max2? sum1: sum2;        for (int i = 0; i < length - 2; i++) {            int p = i+1;            int q = length - 1;            while (p < q) {                int sum = numList.get(i) + numList.get(p) + numList.get(q);                int dis = distance(sum, target);                if (dis == 0) {                    return target;                }                if (dis < max) {                    targetSum = sum;                    max = dis;                }                if (sum < target) {                    p++;                } else {                    q--;                }            }        }        return targetSum;    }        private int distance(int source, int target) {        if (source > target) {            return source - target;        } else {            return target - source;        }    }}