PowerPoint Presentation - Day 3: The Command and Visitor Patterns

List Sort

•class Cons extends List {

• Object first;

• List rest;

• Cons(Object f, List r) {

• first = f;

• rest = r;

• }

• Object getFirst() { return first; }

• List getRest() { return rest; }

• List insert(Object e) {

• Comparable ce = (Comparable) e;

• Comparable cf = (Comparable) first;

• if (ce.compareTo(cf) < 0) return new Cons(e,this);

• else return new Cons(first, rest.insert(e));

• }

•

• List sort() { return rest.sort().insert(first); }

•

• public String toString() {

• // no leading space before first

• return "(" + first + rest.toStringHelp() + ")";

• }

• String toStringHelp() {

• // leading space before each elt

• return " " + first + rest.toStringHelp();

• }

•}

•