carfield.com.hk

Aluminum.java

2001-12-26T16:00:00Z

Cardboard.java

2001-12-26T16:00:00Z

DynaTrash.java

2001-12-26T16:00:00Z

//: c12:dynatrash:DynaTrash.java 
// Using a Map of Lists and RTTI
// to automatically sort trash into
// ArrayLists. This solution, despite the
// use of RTTI, is extensible.
import c12.trash.*;
import java.util.*;
import com.bruceeckel.test.*;

// Generic TypeMap works in any situation:
class TypeMap {
  private Map t = new HashMap();
  public void add(Object o) {
    Class type = o.getClass();
    if(t.containsKey(type))
      ((List)t.get(type)).add(o);
    else {
      List v = new ArrayList();
      v.add(o);
      t.put(type,v);
    }
  }
  public List get(Class type) {
    return (List)t.get(type);
  }
  public Iterator keys() { 
    return t.keySet().iterator(); 
  }
}

// Adapter class to allow callbacks
// from ParseTrash.fillBin():
class TypeMapAdapter implements Fillable {
  TypeMap map;
  public TypeMapAdapter(TypeMap tm) { map = tm; }
  public void addTrash(Trash t) { map.add(t); }
}

public class DynaTrash extends UnitTest {
  TypeMap bin = new TypeMap();
  public DynaTrash() {
    ParseTrash.fillBin("../trash/Trash.dat", 
      new TypeMapAdapter(bin));
  }
  public void test() {
    Iterator keys = bin.keys();
    while(keys.hasNext())
      Trash.sumValue(
        bin.get((Class)keys.next()).iterator());
  }
  public static void main(String args[]) {
    new DynaTrash().test();
  }
} ///:~

Fillable.java

2001-12-26T16:00:00Z

FillableCollection.java

2001-12-26T16:00:00Z

FillableVisitor.java

2001-12-26T16:00:00Z

Glass.java

2001-12-26T16:00:00Z

Paper.java

2001-12-26T16:00:00Z

ParseTrash.java

2001-12-26T16:00:00Z

RecycleA.java

2001-12-26T16:00:00Z

//: c12:recyclea:RecycleA.java 
// Recycling with RTTI.
import java.util.*;
import java.io.*;
import com.bruceeckel.test.*;

abstract class Trash {
  private double weight;
  Trash(double wt) { weight = wt; }
  abstract double getValue();
  double getWeight() { return weight; }
  // Sums the value of Trash in a bin:
  static void sumValue(Iterator it) {
    double val = 0.0f;
    while(it.hasNext()) {
      // One kind of RTTI:
      // A dynamically-checked cast
      Trash t = (Trash)it.next();
      // Polymorphism in action:
      val += t.getWeight() * t.getValue();
      System.out.println(
        "weight of " +
        // Using RTTI to get type
        // information about the class:
        t.getClass().getName() +
        " = " + t.getWeight());
    }
    System.out.println("Total value = " + val);
  }
}

class Aluminum extends Trash {
  static double val  = 1.67f;
  Aluminum(double wt) { super(wt); }
  double getValue() { return val; }
  static void setValue(double newval) {
    val = newval;
  }
}

class Paper extends Trash {
  static double val = 0.10f;
  Paper(double wt) { super(wt); }
  double getValue() { return val; }
  static void setValue(double newval) {
    val = newval;
  }
}

class Glass extends Trash {
  static double val = 0.23f;
  Glass(double wt) { super(wt); }
  double getValue() { return val; }
  static void setValue(double newval) {
    val = newval;
  }
}

public class RecycleA extends UnitTest {
  Collection 
    bin = new ArrayList(),
    glassBin = new ArrayList(),
    paperBin = new ArrayList(),
    alBin = new ArrayList();
  public RecycleA() {
    // Fill up the Trash bin:
    for(int i = 0; i < 30; i++)
      switch((int)(Math.random() * 3)) {
        case 0 :
          bin.add(new
            Aluminum(Math.random() * 100));
          break;
        case 1 :
          bin.add(new
            Paper(Math.random() * 100));
          break;
        case 2 :
          bin.add(new
            Glass(Math.random() * 100));
    }
  }
  public void test() {
    Iterator sorter = bin.iterator();
    // Sort the Trash:
    while(sorter.hasNext()) {
      Object t = sorter.next();
      // RTTI to show class membership:
      if(t instanceof Aluminum)
        alBin.add(t);
      if(t instanceof Paper)
        paperBin.add(t);
      if(t instanceof Glass)
        glassBin.add(t);
    }
    Trash.sumValue(alBin.iterator());
    Trash.sumValue(paperBin.iterator());
    Trash.sumValue(glassBin.iterator());
    Trash.sumValue(bin.iterator());
  }
  public static void main(String args[]) {
    new RecycleA().test();
  }
} ///:~

RecycleAP.java

2001-12-26T16:00:00Z

//: c12:recycleap:RecycleAP.java 
// Recycling with RTTI and Prototypes.
import c12.trash.*;
import java.util.*;
import com.bruceeckel.test.*;

public class RecycleAP extends UnitTest {
  Collection
    bin = new ArrayList(), 
    glassBin = new ArrayList(),
    paperBin = new ArrayList(),
    alBin = new ArrayList();
  public RecycleAP() {
    // Fill up the Trash bin:
    ParseTrash.fillBin(
      "../trash/Trash.dat", bin);
  }
  public void test() {
    Iterator sorter = bin.iterator();
    // Sort the Trash:
    while(sorter.hasNext()) {
      Object t = sorter.next();
      // RTTI to show class membership:
      if(t instanceof Aluminum)
        alBin.add(t);
      if(t instanceof Paper)
        paperBin.add(t);
      if(t instanceof Glass)
        glassBin.add(t);
    }
    Trash.sumValue(alBin.iterator());
    Trash.sumValue(paperBin.iterator());
    Trash.sumValue(glassBin.iterator());
    Trash.sumValue(bin.iterator());
  }
  public static void main(String args[]) {
    new RecycleAP().test();
  }
} ///:~

RecycleB.java

2001-12-26T16:00:00Z

//: c12:recycleb:RecycleB.java
// Containers that grab objects of interest.
import c12.trash.*;
import java.util.*;
import com.bruceeckel.test.*;

// A container that admits only the right type
// of Trash (established in the constructor):
class Tbin {
  private Collection list = new ArrayList();
  private Class type;
  public Tbin(Class binType) { type = binType; }
  public boolean grab(Trash t) {
    // Comparing class types:
    if(t.getClass().equals(type)) {
      list.add(t);
      return true; // Object grabbed
    }
    return false; // Object not grabbed
  }
  public Iterator iterator() {
    return list.iterator();
  }
}

class TbinList extends ArrayList {
  void sort(Trash t) {
    Iterator e = iterator(); // Iterate over self
    while(e.hasNext())
      if(((Tbin)e.next()).grab(t)) return;
    // Need a new Tbin for this type:
    add(new Tbin(t.getClass()));
    sort(t); // Recursive call
  }
}

public class RecycleB extends UnitTest {
  Collection bin = new ArrayList();
  TbinList trashBins = new TbinList();
  public RecycleB() {
    ParseTrash.fillBin("../trash/Trash.dat",bin);
  }
  public void test() {
    Iterator it = bin.iterator();
    while(it.hasNext())
      trashBins.sort((Trash)it.next());
    Iterator e = trashBins.iterator();
    while(e.hasNext()) {
      Tbin b = (Tbin)e.next();
      Trash.sumValue(b.iterator());
    }
    Trash.sumValue(bin.iterator());
  }
  public static void main(String args[]) {
    new RecycleB().test();
  }
} ///:~

Trash.dat

2001-12-26T16:00:00Z

Trash.java

2001-12-26T16:00:00Z

//: c12:trash:Trash.java
// Base class for Trash recycling examples.
package c12.trash;
import java.util.*;
import java.lang.reflect.*;

public abstract class Trash {
  private double weight;
  public Trash(double wt) { weight = wt; }
  public Trash() {}
  public abstract double getValue();
  public double getWeight() { return weight; }
  // Sums the value of Trash given an
  // Iterator to any container of Trash:
  public static void sumValue(Iterator it) {
    double val = 0.0f;
    while(it.hasNext()) {
      // One kind of RTTI:
      // A dynamically-checked cast
      Trash t = (Trash)it.next();
      val += t.getWeight() * t.getValue();
      System.out.println(
        "weight of " +
        // Using RTTI to get type
        // information about the class:
        t.getClass().getName() +
        " = " + t.getWeight());
    }
    System.out.println("Total value = " + val);
  }
  // Remainder of class provides 
  // support for prototyping:
  private static List trashTypes = 
    new ArrayList();
  public static Trash factory(Messenger info) {
    for(int i = 0; i < trashTypes.size(); i++) {
      // Somehow determine the new type
      // to create, and create one:
      Class tc = (Class)trashTypes.get(i);
      if (tc.getName().indexOf(info.id) != -1) {
        try {
          // Get the dynamic constructor method
          // that takes a double argument:
          Constructor ctor = tc.getConstructor(
              new Class[]{ double.class });
          // Call the constructor  
          // to create a new object:
          return (Trash)ctor.newInstance(
            new Object[]{new Double(info.data)});
        } catch(Exception ex) {
          ex.printStackTrace(System.err);
          throw new RuntimeException(
            "Cannot Create Trash");
        }
      }
    }
    // Class was not in the list. Try to load it,
    // but it must be in your class path!
    try {
      System.out.println("Loading " + info.id);
      trashTypes.add(Class.forName(info.id));
    } catch(Exception e) {
      e.printStackTrace(System.err);
      throw new RuntimeException(
        "Prototype not found");
    }
    // Loaded successfully. 
    // Recursive call should work:
    return factory(info);
  }
  public static class Messenger {
    public String id;
    public double data;
    public Messenger(String name, double val) {
      id = name;
      data = val;
    }
  }
} ///:~

TrashVisitor.java

2001-12-26T16:00:00Z

//: c12:trashvisitor:TrashVisitor.java 
// The "visitor" pattern with VisitableDecorators.
import c12.trash.*;
import java.util.*;
import com.bruceeckel.test.*;

// Specific group of algorithms packaged
// in each implementation of Visitor:
class PriceVisitor implements Visitor {
  private double alSum; // Aluminum
  private double pSum; // Paper
  private double gSum; // Glass
  private double cSum; // Cardboard
  public void visit(Aluminum al) {
    double v = al.getWeight() * al.getValue();
    System.out.println(
      "value of Aluminum= " + v);
    alSum += v;
  }
  public void visit(Paper p) {
    double v = p.getWeight() * p.getValue();
    System.out.println(
      "value of Paper= " + v);
    pSum += v;
  }
  public void visit(Glass g) {
    double v = g.getWeight() * g.getValue();
    System.out.println(
      "value of Glass= " + v);
    gSum += v;
  }
  public void visit(Cardboard c) {
    double v = c.getWeight() * c.getValue();
    System.out.println(
      "value of Cardboard = " + v);
    cSum += v;
  }
  void total() {
    System.out.println(
      "Total Aluminum: $" + alSum +
      "\n Total Paper: $" + pSum + 
      "\nTotal Glass: $" + gSum + 
      "\nTotal Cardboard: $" + cSum +
      "\nTotal: $" + 
        (alSum + pSum + gSum + cSum));
  }
}

class WeightVisitor implements Visitor {
  private double alSum; // Aluminum
  private double pSum; // Paper
  private double gSum; // Glass
  private double cSum; // Cardboard
  public void visit(Aluminum al) {
    alSum += al.getWeight();
    System.out.println("weight of Aluminum = "
        + al.getWeight());
  }
  public void visit(Paper p) {
    pSum += p.getWeight();
    System.out.println("weight of Paper = "
        + p.getWeight());
  }
  public void visit(Glass g) {
    gSum += g.getWeight();
    System.out.println("weight of Glass = "
        + g.getWeight());
  }
  public void visit(Cardboard c) {
    cSum += c.getWeight();
    System.out.println("weight of Cardboard = "
        + c.getWeight());
  }
  void total() {
    System.out.println(
      "Total weight Aluminum: "  + alSum +
      "\nTotal weight Paper: " + pSum +
      "\nTotal weight Glass: " + gSum +
      "\nTotal weight Cardboard: " + cSum +
      "\nTotal weight: " + 
        (alSum + pSum + gSum + cSum));

  }
}

public class TrashVisitor extends UnitTest {
  Collection bin = new ArrayList();
  PriceVisitor pv = new PriceVisitor();
  WeightVisitor wv = new WeightVisitor();
  public TrashVisitor() {
    ParseTrash.fillBin("../trash/Trash.dat", 
      new FillableVisitor(
        new FillableCollection(bin)));
  }
  public void test() {
    Iterator it = bin.iterator();
    while(it.hasNext()) {
      Visitable v = (Visitable)it.next();
      v.accept(pv);
      v.accept(wv);
    }
    pv.total();
    wv.total();
  }
  public static void main(String args[]) {
    new TrashVisitor().test();
  }
} ///:~

VAluminum.java

2001-12-26T16:00:00Z

Visitable.java

2001-12-26T16:00:00Z

VisitableDecorator.java

2001-12-26T16:00:00Z

Visitor.java

2001-12-26T16:00:00Z

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 .\c12\trashvisitor
# 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: \
	Visitable.class \
	Visitor.class \
	VAluminum.class \
	VisitableDecorator.class \
	FillableVisitor.class \
	TrashVisitor.class

jikes: \
	Visitable.class \
	Visitor.class \
	VAluminum.class \
	VisitableDecorator.class \
	FillableVisitor.class \
	TrashVisitor.class

clean:
ifeq ($(notdir $(SHELL)),COMMAND.COM)
	del *.class
else
	rm -f *.class
endif


Visitable.class: Visitable.java 

Visitor.class: Visitor.java 

VAluminum.class: VAluminum.java 

VisitableDecorator.class: VisitableDecorator.java 

FillableVisitor.class: FillableVisitor.java 

TrashVisitor.class: TrashVisitor.java 
	$(JVC) $(JVCFLAGS) $<
	java com.bruceeckel.test.RunUnitTests TrashVisitor