Kotlin slower than java by around 100x for equivalent code

205

I was solving this problem https://leetcode.com/problems/longest-substring-without-repeating-characters/

I submitted a kotlin solution which had runtime of 190ms and then I just converted this code to java code and the runtime was 2ms. Why is this the case?

Following is my kotlin code

class Solution {
  fun lengthOfLongestSubstring(s:String):Int {
    val exists = BooleanArray(256)
    var i = 0
    var j = 0
    var ans = 0
    while (j < s.length) {
      if (!exists[s.get(j).toInt()]) {
        exists[s.get(j).toInt()] = true
        j++
        ans = Math.max(ans, j - i)
      } else {
        exists[s.get(i).toInt()] = false
        i++
      }
    }
    return ans
  }
}

And following is my java code

class Solution {
    public int lengthOfLongestSubstring(String s) {
        boolean[] exists = new boolean[256];
        int i = 0, j = 0, ans = 0;
        while (j < s.length()) {
            if (!exists[(int) s.charAt(j)]) {
                exists[(int) s.charAt(j)] = true;
                j++;
                ans = Math.max(ans, j - i);
            } else {
                exists[(int) s.charAt(i)] = false;
                i++;
            }
        }
        return ans;
    }
}

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