//: TrashVisitor.java
//////////////////////////////////////////////////
// Copyright (c) Bruce Eckel, 1998
// Source code file from the book "Thinking in Java"
// All rights reserved EXCEPT as allowed by the
// following statements: You can freely use this file
// for your own work (personal or commercial),
// including modifications and distribution in
// executable form only. Permission is granted to use
// this file in classroom situations, including its
// use in presentation materials, as long as the book
// "Thinking in Java" is cited as the source.
// Except in classroom situations, you cannot copy
// and distribute this code; instead, the sole
// distribution point is http://www.BruceEckel.com
// (and official mirror sites) where it is
// freely available. You cannot remove this
// copyright and notice. You cannot distribute
// modified versions of the source code in this
// package. You cannot use this file in printed
// media without the express permission of the
// author. Bruce Eckel makes no representation about
// the suitability of this software for any purpose.
// It is provided "as is" without express or implied
// warranty of any kind, including any implied
// warranty of merchantability, fitness for a
// particular purpose or non-infringement. The entire
// risk as to the quality and performance of the
// software is with you. Bruce Eckel and the
// publisher shall not be liable for any damages
// suffered by you or any third party as a result of
// using or distributing software. In no event will
// Bruce Eckel or the publisher be liable for any
// lost revenue, profit, or data, or for direct,
// indirect, special, consequential, incidental, or
// punitive damages, however caused and regardless of
// the theory of liability, arising out of the use of
// or inability to use software, even if Bruce Eckel
// and the publisher have been advised of the
// possibility of such damages. Should the software
// prove defective, you assume the cost of all
// necessary servicing, repair, or correction. If you
// think you've found an error, please email all
// modified files with clearly commented changes to:
// Bruce@EckelObjects.com. (Please use the same
// address for non-code errors found in the book.)
/////////////////////////////////////////////////
// The "visitor" pattern
package c16.trashvisitor;
import c16.trash.*;
import java.util.*;
// 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(VAluminum al) {
double v = al.weight() * al.value();
System.out.println(
"value of Aluminum= " + v);
alSum += v;
}
public void visit(VPaper p) {
double v = p.weight() * p.value();
System.out.println(
"value of Paper= " + v);
pSum += v;
}
public void visit(VGlass g) {
double v = g.weight() * g.value();
System.out.println(
"value of Glass= " + v);
gSum += v;
}
public void visit(VCardboard c) {
double v = c.weight() * c.value();
System.out.println(
"value of Cardboard = " + v);
cSum += v;
}
void total() {
System.out.println(
"Total Aluminum: $" + alSum + "\n" +
"Total Paper: $" + pSum + "\n" +
"Total Glass: $" + gSum + "\n" +
"Total Cardboard: $" + cSum);
}
}
class WeightVisitor implements Visitor {
private double alSum; // Aluminum
private double pSum; // Paper
private double gSum; // Glass
private double cSum; // Cardboard
public void visit(VAluminum al) {
alSum += al.weight();
System.out.println("weight of Aluminum = "
+ al.weight());
}
public void visit(VPaper p) {
pSum += p.weight();
System.out.println("weight of Paper = "
+ p.weight());
}
public void visit(VGlass g) {
gSum += g.weight();
System.out.println("weight of Glass = "
+ g.weight());
}
public void visit(VCardboard c) {
cSum += c.weight();
System.out.println("weight of Cardboard = "
+ c.weight());
}
void total() {
System.out.println("Total weight Aluminum:"
+ alSum);
System.out.println("Total weight Paper:"
+ pSum);
System.out.println("Total weight Glass:"
+ gSum);
System.out.println("Total weight Cardboard:"
+ cSum);
}
}
public class TrashVisitor {
public static void main(String[] args) {
Vector bin = new Vector();
// ParseTrash still works, without changes:
ParseTrash.fillBin("VTrash.dat", bin);
// You could even iterate through
// a list of visitors!
PriceVisitor pv = new PriceVisitor();
WeightVisitor wv = new WeightVisitor();
Enumeration it = bin.elements();
while(it.hasMoreElements()) {
Visitable v = (Visitable)it.nextElement();
v.accept(pv);
v.accept(wv);
}
pv.total();
wv.total();
}
} ///:~ |