ReplaceThe.java

@Override
public String replaceThe(String str) {
  
  StringBuilder res = new StringBuilder();
  String vo = "aeiou";

  String[] part = str.split("the");
  res.append(part[0]);
  for (int i = 1; i < part.length; i++) {
    if (vo.contains(part[i].trim().charAt(0) + "")) {
      res.append("an");
    } else {
      res.append("a");
    }
    res.append(part[i]);
  }

  return res.toString();
}

@Override
public String longestZero(String str) {

  String result = "";
  for (String s : str.split("1+")) {
    if (result.length() < s.length()) {
      result = s;
    }
  }
  return result;
}