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Java Source | 2000-05-25 | 5.0 KB | 149 lines |
- //: 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();
- }
- } ///:~