Number of Laser Beams in a Bank LeetCode solution in Java

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class Solution {
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  public int numberOfBeams(String[] bank) {
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    int ans = 0, pre = 0;
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    for (int i = 0; i < bank.length; i++) {
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      int n = 0;
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      for (int j = 0; j < bank[i].length(); j++) if (bank[i].charAt(j) == '1') n++;
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      if (n == 0) continue;
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      ans += pre * n;
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      ;
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      pre = n;
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    }
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    return ans;
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  }
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}