Program: 101045
Project: 101045
Buggy source:
@Override public Iterable<String> predictiveSearch(String prefix){
  List<String> ret=new ArrayList<String>();
  StringBuilder current=new StringBuilder();
  char[] chars=prefix.toCharArray();
  int nodeIndex=0;
  TailCharIterator it=new TailCharIterator(tails,-1);
  for (int i=0; i < chars.length; i++) {
    int ti=tail[nodeIndex];
    if (ti != -1) {
      int first=i;
      it.setIndex(ti);
      do {
        if (!it.hasNext())         break;
        if (it.next() != chars[i])         return ret;
        i++;
      }
 while (i < chars.length);
      if (i >= chars.length)       break;
      current.append(chars,first,i - first);
    }
    int cid=findCharId(chars[i]);
    if (cid == -1)     return ret;
    int next=base[nodeIndex] + cid;
    if (next < 0 || check.length <= next || (next + check[next]) != nodeIndex)     return ret;
    nodeIndex=next;
    current.append(chars[i]);
  }
  Deque<Pair<Integer,char[]>> q=new LinkedList<Pair<Integer,char[]>>();
  q.add(Pair.create(nodeIndex,current.toString().toCharArray()));
  while (!q.isEmpty()) {
    Pair<Integer,char[]> p=q.pop();
    int ni=p.getFirst();
    StringBuilder buff=new StringBuilder().append(p.getSecond());
    int ti=tail[ni];
    if (ti != -1) {
      it.setIndex(ti);
      while (it.hasNext()) {
        buff.append(it.next());
      }
    }
    if (term.get(ni))     ret.add(buff.toString());
    for (    Map.Entry<Character,Integer> e : charCodes.entrySet()) {
      int b=base[ni];
      if (b == BASE_EMPTY)       continue;
      int next=b + e.getValue();
      if (check.length <= next)       continue;
      if (next + check[next] == ni) {
        StringBuilder bu=new StringBuilder(buff);
        bu.append(e.getKey());
        q.push(Pair.create(next,bu.toString().toCharArray()));
      }
    }
  }
  return ret;
}

Fixed version (ground truth):
@Override public Iterable<String> predictiveSearch(String prefix){
  List<String> ret=new ArrayList<String>();
  StringBuilder current=new StringBuilder();
  char[] chars=prefix.toCharArray();
  int nodeIndex=0;
  TailCharIterator it=new TailCharIterator(tails,-1);
  for (int i=0; i < chars.length; i++) {
    int ti=tail[nodeIndex];
    if (ti != -1) {
      int first=i;
      it.setIndex(ti);
      do {
        if (!it.hasNext())         break;
        if (it.next() != chars[i])         return ret;
        i++;
      }
 while (i < chars.length);
      if (i >= chars.length)       break;
      current.append(chars,first,i - first);
    }
    int cid=findCharId(chars[i]);
    if (cid == -1)     return ret;
    int next=base[nodeIndex] + cid;
    if (next < 0 || check.length <= next || (next + check[next]) != nodeIndex)     return ret;
    nodeIndex=next;
    current.append(chars[i]);
  }
  Deque<Pair<Integer,char[]>> q=new LinkedList<Pair<Integer,char[]>>();
  q.add(Pair.create(nodeIndex,current.toString().toCharArray()));
  while (!q.isEmpty()) {
    Pair<Integer,char[]> p=q.pop();
    int ni=p.getFirst();
    StringBuilder buff=new StringBuilder().append(p.getSecond());
    int ti=tail[ni];
    if (ti != -1) {
      it.setIndex(ti);
      while (it.hasNext()) {
        buff.append(it.next());
      }
    }
    if (term.get(ni))     ret.add(buff.toString());
    for (    Map.Entry<Character,Integer> e : charCodes.entrySet()) {
      int b=base[ni];
      if (b == BASE_EMPTY)       continue;
      if (b == (BASE_EMPTY - 1))       continue;
      int next=b + e.getValue();
      if (check.length <= next)       continue;
      if (next + check[next] == ni) {
        StringBuilder bu=new StringBuilder(buff);
        bu.append(e.getKey());
        q.push(Pair.create(next,bu.toString().toCharArray()));
      }
    }
  }
  return ret;
}