Convert a Number to Hexadecimal LeetCode solution in Java

1
class Solution {
2
  public String toHex(int num) {
3
    if (num == 0) return "0";
4

5
    boolean start = true;
6

7
    StringBuilder sb = new StringBuilder();
8

9
    for (int i = 28; i >= 0; i -= 4) {
10
      int digit = (num >> i) & 15;
11
      if (digit > 9) {
12
        char curr = (char) (digit % 10 + 'a');
13
        sb.append(curr);
14
        start = false;
15
      } else if (digit != 0) {
16
        char curr = (char) (digit + '0');
17
        sb.append(curr);
18
        start = false;
19
      } else { // digit == 0
20
        if (start == false) { // avoid case: 00001a
21
          sb.append('0');
22
        }
23
      }
24
    }
25
    return sb.toString();
26
  }
27
}