peek method
Implementation
String peek(int length) {
if (length < 0) {
return "";
}
if (!canTake(length)) {
throw StateError("Not enough characters in queue to peek $length");
}
StringBuffer sb = StringBuffer();
for (String piece in queue) {
if (sb.length + piece.length > length) {
break;
}
sb.write(piece);
}
return sb.toString();
}