License Key Formatting LeetCode solution in Java

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class Solution {
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  public String licenseKeyFormatting(String s, int k) {
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    StringBuilder answer = new StringBuilder();
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    int length = 0;
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    // Iterate Backwards to fullfill first group condition
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    for (int i = s.length() - 1; i >= 0; i--) {
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      if (s.charAt(i) == '-') {
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        continue;
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      }
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      if (length > 0 && length % k == 0) {
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        answer.append('-');
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      }
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      answer.append(Character.toUpperCase(s.charAt(i)));
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      length++;
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    }
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    return answer.reverse().toString();
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  }
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}