Parse delimited integer list

public static List<Integer> parseIntegerList(CharSequence text) {
if (text == null) {
return new ArrayList();
} else {
List<Integer> list = new ArrayList();
StringBuilder builder1 = new StringBuilder();
StringBuilder builder2 = new StringBuilder();
boolean noRangeSeparator = true;
for (int a = 0; a <= text.length(); a++) {
final char c = (a < text.length()) ? (text.charAt(a)) : (',');
if (Character.isDigit(c)) {
if (noRangeSeparator) {
builder1.append(c);
} else {
builder2.append(c);
}
} else if (c == '-') {
if (noRangeSeparator) {
noRangeSeparator = false;
} else {
throw new IllegalArgumentException("Invalid [text] argument: second range separator");
}
} else if (c == ',') {
if (noRangeSeparator) {
if (builder1.length() > 0) {
list.add(Integer.parseInt(builder1.toString()));
}
} else {
if (builder2.length() == 0) {
throw new IllegalArgumentException("Invalid [text] argument: invalid range");
} else if (builder1.length() == 0) {
list.add(Integer.parseInt("-" + builder2.toString()));
} else {
final int start = Integer.parseInt(builder1.toString());
final int end = Integer.parseInt(builder2.toString());
if (end < start) {
throw new IllegalArgumentException("Invalid [text] argument: invalid range");
}
for (int b = start; b <= end; b++) {
list.add(b);
}
}
}
builder1 = new StringBuilder();
builder2 = new StringBuilder();
noRangeSeparator = true;
} else if ((!Character.isWhitespace(c)) && (!Character.isISOControl(c))) {
throw new IllegalArgumentException("Invalid [text] argument: contains illegal characters");
}
}
return list;
}
}