Longest Valid Parentheses LeetCode solution in Java

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class Solution {
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  public int longestValidParentheses(String s) {
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    int i = 0;
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    int len = 0;
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    while (i < s.length()) {
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      int j = i;
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      int open = 0;
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      int closed = 0;
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      while (j < s.length()) {
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        char ch = s.charAt(j);
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        if (ch == '(') open++;
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        if (ch == ')') closed++;
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        if (closed > open) break;
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        if (open == closed) len = Math.max(len, j - i + 1);
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        j++;
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      }
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      i++;
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    }
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    return len;
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  }
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}