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();

}