Program: 39971
Project: 39971
Buggy source:
public void rebuild(String expression) throws ParsingException {
  Integer pos;
  Character currentPrev;
  Character prevAtRebuilded;
  if (expression == null) {
    throw new ParsingException("String_Node_Str",new NullPointerException());
  }
  expression=expression.replace("String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str");
  expression='#' + expression + '#';
  Stack<Character> temp=new Stack<>();
  temp.add('#');
  pos=1;
  currentPrev='#';
  prevAtRebuilded=currentPrev;
  while (!temp.isEmpty()) {
    char symbol=expression.charAt(pos);
    if ("String_Node_Str".indexOf(symbol) != -1) {
      fstPriorityHandler(symbol,pos,currentPrev,prevAtRebuilded,temp);
      continue;
    }
    if ("String_Node_Str".indexOf(symbol) != -1) {
      sndPriorityHandler(symbol,pos,currentPrev,prevAtRebuilded,temp);
      continue;
    }
    if (symbol == '(') {
      temp.add(symbol);
      currentPrev=symbol;
      pos++;
      continue;
    }
    if (symbol == ')') {
      closeBrace(pos,currentPrev,prevAtRebuilded,temp);
      continue;
    }
    if (symbol == '#') {
      endSymbol(pos,currentPrev,prevAtRebuilded,temp);
      continue;
    }
    if (NUMBERS.indexOf(symbol) != -1) {
      rebuildedExpression+=symbol;
      prevAtRebuilded=symbol;
      currentPrev=symbol;
      pos++;
    }
 else {
      throw new ParsingException("String_Node_Str");
    }
  }
  if (rebuildedExpression.equals("String_Node_Str")) {
    throw new ParsingException("String_Node_Str");
  }
  String tmp="String_Node_Str";
  for (int i=0; i < rebuildedExpression.length(); i++) {
    if ("String_Node_Str".indexOf(rebuildedExpression.charAt(i)) == -1) {
      while (temp.size() != 1 && !temp.isEmpty()) {
        char a=temp.pop();
        char b=temp.pop();
        if (a == b) {
          temp.add('+');
        }
 else {
          temp.add('-');
        }
      }
      if (temp.size() == 1) {
        tmp+=temp.pop();
      }
      tmp+=rebuildedExpression.charAt(i);
    }
 else {
      temp.add(rebuildedExpression.charAt(i));
    }
  }
  rebuildedExpression=tmp;
}

Fixed version (ground truth):
public void rebuild(String expression) throws ParsingException {
  if (expression == null) {
    throw new ParsingException("String_Node_Str",new NullPointerException());
  }
  expression=expression.replace("String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str");
  expression='#' + expression + '#';
  Stack<Character> temp=new Stack<>();
  temp.add('#');
  pos=1;
  currentPrev='#';
  prevAtRebuilded=currentPrev;
  while (!temp.isEmpty()) {
    char symbol=expression.charAt(pos);
    if ("String_Node_Str".indexOf(symbol) != -1) {
      fstPriorityHandler(symbol,temp);
      continue;
    }
    if ("String_Node_Str".indexOf(symbol) != -1) {
      sndPriorityHandler(symbol,temp);
      continue;
    }
    if (symbol == '(') {
      temp.add(symbol);
      currentPrev=symbol;
      pos++;
      continue;
    }
    if (symbol == ')') {
      closeBrace(temp);
      continue;
    }
    if (symbol == '#') {
      endSymbol(temp);
      continue;
    }
    if (NUMBERS.indexOf(symbol) != -1) {
      rebuildedExpression+=symbol;
      prevAtRebuilded=symbol;
      currentPrev=symbol;
      pos++;
    }
 else {
      throw new ParsingException("String_Node_Str");
    }
  }
  if (rebuildedExpression.equals("String_Node_Str")) {
    throw new ParsingException("String_Node_Str");
  }
  String tmp="String_Node_Str";
  for (int i=0; i < rebuildedExpression.length(); i++) {
    if ("String_Node_Str".indexOf(rebuildedExpression.charAt(i)) == -1) {
      while (temp.size() != 1 && !temp.isEmpty()) {
        char a=temp.pop();
        char b=temp.pop();
        if (a == b) {
          temp.add('+');
        }
 else {
          temp.add('-');
        }
      }
      if (temp.size() == 1) {
        tmp+=temp.pop();
      }
      tmp+=rebuildedExpression.charAt(i);
    }
 else {
      temp.add(rebuildedExpression.charAt(i));
    }
  }
  rebuildedExpression=tmp;
}