@Override
	public int compareTo(Field o) {
		StringField f = (StringField) o;
		if (str == null) {
			if (f.str == null) {
				return 0;
			}
			return -1;
		}
		else if (f.str == null) {
			return 1;
		}
		return str.compareTo(f.str);
	}
Construct a String field with an initial value of s.
@param str initial string value or null
@param immutable true if field value is immutable
Ghidra/Framework/DB/src/main/java/db/StringField.java