PowerPoint Presentation - Composite and Interpreter Pattern

Singleton IntList

•import java.util.NoSuchElementException;

•

•abstract class IntList {

• abstract int getFirst();

• abstract IntList getRest();

•}

•

•class Empty extends IntList {

• static final Empty ONLY = new Empty();

• private Empty() {}

• int getFirst() {

• throw new

• NoSuchElementException("getFirst applied to Empty()");

• }

• int getRest() {

• throw new

• NoSuchElementException("getRest applied to Empty()");

• }

• public String toString() { return "Empty()"; }

•}

•

•class NonEmpty extends IntList {

• int first;

• IntList rest;

• int getFirst() { return first; );

• IntList getRest() { return rest; }

• public String toString() { return "NonEmpty(" + first + ", " + rest + ")"; }

•}

•

Static member holding the unique instance

Private constructor