Check If String Is a Prefix of Array LeetCode solution in Java

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class Solution {
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  public boolean isPrefixString(String s, String[] words) {
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    StringBuilder res = new StringBuilder("");
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    for (String word : words) {
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      res.append(word);
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      if (s.equals(res.toString())) return true;
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      if (s.indexOf(res.toString()) == -1) return false;
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    }
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    return false;
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  }
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}