Find Smallest Letter Greater Than Target LeetCode solution in Java

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class Solution {
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  public char nextGreatestLetter(char[] letters, char target) {
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    char res = letters[0];
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    int start = 0;
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    int end = letters.length - 1;
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    while (start <= end) {
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      int mid = start + (end - start) / 2;
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      if (letters[mid] == target) {
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        start = mid + 1;
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      } else if (target > letters[mid]) {
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        start = mid + 1;
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      } else if (letters[mid] > target) {
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        res = letters[mid];
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        end = mid - 1;
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      }
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    }
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    return res;
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  }
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}