carfield.com.hk

BeeAndFlowers.java

2001-12-26T16:00:00Z

//: c11:BeeAndFlowers.java
// Demonstration of "visitor" pattern.
import java.util.*;
import com.bruceeckel.test.*;

interface Visitor {  
  void visit(Gladiolus g);
  void visit(Renuculus r);
  void visit(Chrysanthemum c);
}

// The Flower hierarchy cannot be changed:
interface Flower {  
  void accept(Visitor v);
}

class Gladiolus implements Flower {  
  public void accept(Visitor v) { v.visit(this);}
}

class Renuculus implements Flower {  
  public void accept(Visitor v) { v.visit(this);}
}

class Chrysanthemum implements Flower {  
  public void accept(Visitor v) { v.visit(this);}
}

// Add the ability to produce a string:
class StringVal implements Visitor {
  String s;  
  public String toString() { return s; }
  public void visit(Gladiolus g) { 
    s = "Gladiolus"; 
  }
  public void visit(Renuculus r) { 
    s = "Renuculus"; 
  }
  public void visit(Chrysanthemum c) { 
    s = "Chrysanthemum"; 
  }
}

// Add the ability to do "Bee" activities:
class Bee implements Visitor {  
  public void visit(Gladiolus g) {
    System.out.println("Bee and Gladiolus");
  }
  public void visit(Renuculus r) {
    System.out.println("Bee and Renuculus");
  }
  public void visit(Chrysanthemum c) {
    System.out.println("Bee and Chrysanthemum");
  }
}

class FlowerGenerator {
  public static Flower newFlower() {
    switch((int)(Math.random() * 3)) {
      default:
      case 0: return new Gladiolus();
      case 1: return new Renuculus();
      case 2: return new Chrysanthemum();
    }
  }
}

public class BeeAndFlowers extends UnitTest {
  List flowers = new ArrayList();
  public BeeAndFlowers() {
    for(int i = 0; i < 10; i++)
      flowers.add(FlowerGenerator.newFlower());
  }
  public void test() {
    // It's almost as if I had a function to
    // produce a Flower string representation:
    StringVal sval = new StringVal();
    Iterator it = flowers.iterator();
    while(it.hasNext()) {
      ((Flower)it.next()).accept(sval);
      System.out.println(sval);
    }
    // Perform "Bee" operation on all Flowers:
    Bee bee = new Bee();
    it = flowers.iterator();
    while(it.hasNext())
      ((Flower)it.next()).accept(bee);
  }
  public static void main(String args[]) {
    new BeeAndFlowers().test();
  }
} ///:~

PaperScissorsRock.java

2001-12-26T16:00:00Z

//: c11:PaperScissorsRock.java
// Demonstration of multiple dispatching.
import java.util.*;
import com.bruceeckel.test.*;

// An enumeration type:
class Outcome {
  private int value;
  private String name;
  private Outcome(int val, String nm) { 
    value = val;
    name = nm;
  }
  public final static Outcome
    WIN = new Outcome(0, "win"), 
    LOSE = new Outcome(1, "lose"), 
    DRAW = new Outcome(2, "draw");
  public String toString() { return name; }
  public boolean equals(Object o) {
    return (o instanceof Outcome)
      && (value == ((Outcome)o).value);
  }
}

interface Item {
  Outcome compete(Item it);
  Outcome eval(Paper p);
  Outcome eval(Scissors s);
  Outcome eval(Rock r);
}

class Paper implements Item {
  public Outcome compete(Item it) {
    return it.eval(this);
  }
  public Outcome eval(Paper p) {
    return Outcome.DRAW;
  }
  public Outcome eval(Scissors s) {
    return Outcome.WIN;
  }
  public Outcome eval(Rock r) {
    return Outcome.LOSE;
  }
  public String toString() { return "Paper"; }
}

class Scissors implements Item {
  public Outcome compete(Item it) {
    return it.eval(this);
  }
  public Outcome eval(Paper p) {
    return Outcome.LOSE;
  }
  public Outcome eval(Scissors s) {
    return Outcome.DRAW;
  }
  public Outcome eval(Rock r) {
    return Outcome.WIN;
  }
  public String toString() { return "Scissors"; }
}

class Rock implements Item {
  public Outcome compete(Item it) {
    return it.eval(this);
  }
  public Outcome eval(Paper p) {
    return Outcome.WIN;
  }
  public Outcome eval(Scissors s) {
    return Outcome.LOSE;
  }
  public Outcome eval(Rock r) {
    return Outcome.DRAW;
  }
  public String toString() { return "Rock"; }
}

class ItemGenerator {
  public static Item newItem() {
    switch((int)(Math.random() * 3)) {
      default:
      case 0:
        return new Scissors();
      case 1:
        return new Paper();
      case 2:
        return new Rock();
    }
  }
}

class Compete {
  public static Outcome match(Item a, Item b) {
    System.out.print(a + " <--> " + b + " : ");
    return a.compete(b);
  }
}

public class PaperScissorsRock extends UnitTest {
  List 
    items1 = new ArrayList(),
    items2 = new ArrayList();
  static int SIZE = 20;
  public PaperScissorsRock() {
    for(int i = 0; i < SIZE; i++) {
      items1.add(ItemGenerator.newItem());
      items2.add(ItemGenerator.newItem());
    }
  }
  public void test() {
    for(int i = 0; i < SIZE; i++)
      System.out.println(
        Compete.match(
          (Item)items1.get(i), 
          (Item)items2.get(i)));
  }
  public static void main(String args[]) {
    new PaperScissorsRock().test();
  }
} ///:~

makefile

2001-12-26T16:00:00Z

# From Thinking in Patterns (with Java) by Bruce Eckel
# At http://www.BruceEckel.com
# (c)2001 Bruce Eckel 
# Copyright notice in Copyright.txt
# Automatically-generated MAKEFILE 
# For examples in directory .\c11
# using the JDK 1.3 compiler
# Invoke with: make

HOME := ../

ifndef MAKECMDGOALS
MAKECMDGOALS := javac
endif

# Command.com is too weak to build this under Windows NT/2000:
ifeq ($(OS),Windows_NT)
COMSPEC=$(SYSTEMROOT)\system32\cmd.exe
endif

ifneq ($(MAKECMDGOALS),clean)
include $(HOME)/$(MAKECMDGOALS).mac
endif

.SUFFIXES : .class .java
.java.class :
	$(JVC) $(JVCFLAGS) $<

javac: \
	PaperScissorsRock.class \
	BeeAndFlowers.class

jikes: \
	PaperScissorsRock.class \
	BeeAndFlowers.class

clean:
ifeq ($(notdir $(SHELL)),COMMAND.COM)
	del *.class
else
	rm -f *.class
endif


PaperScissorsRock.class: PaperScissorsRock.java 
	$(JVC) $(JVCFLAGS) $<
	java com.bruceeckel.test.RunUnitTests PaperScissorsRock
BeeAndFlowers.class: BeeAndFlowers.java 
	$(JVC) $(JVCFLAGS) $<
	java com.bruceeckel.test.RunUnitTests BeeAndFlowers