https://leetcode.com/problems/convert-a-number-to-hexadecimal/// https://discuss.leetcode.com/topic/60365/simple-java-solution-with-comment/4public class Solution {    public String toHex(int num) {        char []cmap = {‘0‘,‘1‘,‘2‘,‘3‘,‘4‘,‘5‘,‘6‘,‘7‘,‘8‘,‘9‘,‘a‘,‘b‘,‘c‘,‘d‘,‘e‘,‘f‘};        StringBuilder sb = new StringBuilder();        do {            sb.append(cmap[num & 15]);            num >>>= 4;        } while (num != 0);        return sb.reverse().toString();    }}