Defuse the Bomb LeetCode solution in Java

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class Solution {
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  public int[] decrypt(int[] code, int k) {
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    int[] res = new int[code.length];
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    if (k == 0) return res;
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    // Define the initial window and initial sum
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    int start = 1, end = k, sum = 0;
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    if (k < 0) { // If k < 0, the starting point will be end of the array.
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      k = -k;
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      start = code.length - k;
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      end = code.length - 1;
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    }
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    for (int i = start; i <= end; i++) sum += code[i];
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    // Scan through the code array as i moving to the right, update the window sum.
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    for (int i = 0; i < code.length; i++) {
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      res[i] = sum;
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      sum -= code[(start++) % code.length];
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      sum += code[(++end) % code.length];
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    }
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    return res;
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  }
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}