VisitorPattern

package VisitorPattern;public interface Acceptor {public abstract void accept(Visitor v);}package VisitorPattern;import java.util.Iterator;public abstract class Entry implements Acceptor {public abstract String getName();public abstract int getSize();public Entry add(Entry entry) throws FileTreatmentException{throw new FileTreatmentException();}public Iterator iterator() throws FileTreatmentException{throw new FileTreatmentException();}public String toString(){return getName() + "("+getSize()+")";}}package VisitorPattern;import java.util.Iterator;import java.util.Vector;public class Directory extends Entry{private String name;private Vector dir = new Vector();public Directory(String name){this.name = name;}public String getName(){return name;}public int getSize(){int size = 0;Iterator it = dir.iterator();while(it.hasNext()){Entry entry = (Entry)it.next();size += entry.getSize();}return size;}public Entry add(Entry entry){dir.add(entry);return this;}public Iterator iterator(){return dir.iterator();}public void accept(Visitor v){v.visit(this);}}package VisitorPattern;public class File extends Entry{private String name;private int size;public File(String name,int size){this.name = name;this.size = size;}public int getSize(){return size;}public String getName(){return name;}public void accept(Visitor v){v.visit(this);}}package VisitorPattern;public abstract class Visitor {public abstract void visit(File file);public abstract void visit(Directory directory);}package VisitorPattern;import java.util.Iterator;public class ListVisitor extends Visitor{private String currentdir = "";public void visit(File file){System.out.println(currentdir + "/" + file);}public void visit(Directory directory){System.out.println(currentdir + "/" + directory);String savedir = currentdir;currentdir = currentdir + "/" + directory.getName();Iterator it = directory.iterator();while(it.hasNext()){Entry entry = (Entry)it.next();entry.accept(this);}currentdir = savedir;}}package VisitorPattern;public class FileTreatmentException extends RuntimeException{public FileTreatmentException(){}public FileTreatmentException(String msg){super(msg);}}package VisitorPattern;public class Main {public static void main(String[] args){try {System.out.println("Making root entries...");Directory rootdir = new Directory("root");Directory bindir = new Directory("bin");Directory tmpdir = new Directory("tmp");Directory usrdir = new Directory("usr");rootdir.add(bindir);rootdir.add(tmpdir);rootdir.add(usrdir);bindir.add(new File("vi",1000));bindir.add(new File("latex",2000));rootdir.accept(new ListVisitor());System.out.println("");System.out.println("Making user entries...");Directory yuki = new Directory("yuki");Directory hanako = new Directory("hanako");Directory tomura = new Directory("tomura");usrdir.add(yuki);usrdir.add(hanako);usrdir.add(tomura);yuki.add(new File("diary.html",100));yuki.add(new File("Composizt.java",200));hanako.add(new File("memo.tex",300));tomura.add(new File("game.doc",400));rootdir.accept(new ListVisitor());tomura.add(new File("junk.mail",500));} catch (FileTreatmentException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}