Mega Code Archive
Iterator Pattern 3
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//[C] 2002 Sun Microsystems, Inc.---
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.PrintStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.io.File;
import java.io.IOException;
public class RunIteratorPattern {
public static void main(String [] arguments){
System.out.println("Example for the Iterator pattern");
System.out.println(" This code sample demonstrates how an Iterator can enforce");
System.out.println(" uniformity of processing for different collection types.");
System.out.println(" In this case, there are two classes, ToDoListImpl and");
System.out.println(" ToDoListCollectionImpl, that have different storage needs.");
System.out.println(" ToDoListImpl uses an ArrayList to store its elements in");
System.out.println(" ordered form. The ToDoListCollectionImpl uses a HashMap,");
System.out.println(" since it must differentiate between ToDoListImpl objects by");
System.out.println(" their String identifiers.");
System.out.println();
System.out.println("Although the two classes use different underlying collections,");
System.out.println(" the ListPrinter class can use the Iterator produced by each");
System.out.println(" to print out a set of list contents.");
System.out.println();
if (!(new File("data.ser").exists())){
DataCreator.serialize("data.ser");
}
ToDoListCollection lists = (ToDoListCollection)(DataRetriever.deserializeData("data.ser"));
System.out.println("Lists retrieved. Printing out contents using the Iterator");
System.out.println();
ListPrinter.printToDoListCollection(lists, System.out);
}
}
interface Iterating extends Serializable {
public Iterator getIterator();
}
class ToDoListImpl implements ToDoList {
private String listName;
private ArrayList items = new ArrayList();
public void add(String item) {
if (!items.contains(item)) {
items.add(item);
}
}
public void add(String item, int position) {
if (!items.contains(item)) {
items.add(position, item);
}
}
public void remove(String item) {
if (items.contains(item)) {
items.remove(items.indexOf(item));
}
}
public int getNumberOfItems() {
return items.size();
}
public Iterator getIterator() {
return items.iterator();
}
public String getListName() {
return listName;
}
public void setListName(String newListName) {
listName = newListName;
}
public String toString() {
return listName;
}
}
interface ToDoListCollection extends Iterating {
public void add(ToDoList list);
public void remove(ToDoList list);
public int getNumberOfItems();
}
interface ToDoList extends Iterating {
public void add(String item);
public void add(String item, int position);
public void remove(String item);
public int getNumberOfItems();
public String getListName();
public void setListName(String newListName);
}
class ListPrinter {
public static void printToDoList(ToDoList list, PrintStream output) {
Iterator elements = list.getIterator();
output.println(" List - " + list + ":");
while (elements.hasNext()) {
output.println("\t" + elements.next());
}
}
public static void printToDoListCollection(ToDoListCollection lotsOfLists,
PrintStream output) {
Iterator elements = lotsOfLists.getIterator();
output.println("\"To Do\" List Collection:");
while (elements.hasNext()) {
printToDoList((ToDoList) elements.next(), output);
}
}
public static void printIteratingElement(Iterating element,
PrintStream output) {
output.println("Printing the element " + element);
Iterator elements = element.getIterator();
while (elements.hasNext()) {
Object currentElement = elements.next();
if (currentElement instanceof Iterating) {
printIteratingElement((Iterating) currentElement, output);
output.println();
} else {
output.println(currentElement);
}
}
}
}
class DataRetriever {
public static Object deserializeData(String fileName) {
Object returnValue = null;
try {
File inputFile = new File(fileName);
if (inputFile.exists() && inputFile.isFile()) {
ObjectInputStream readIn = new ObjectInputStream(
new FileInputStream(fileName));
returnValue = readIn.readObject();
readIn.close();
} else {
System.err.println("Unable to locate the file " + fileName);
}
} catch (ClassNotFoundException exc) {
exc.printStackTrace();
} catch (IOException exc) {
exc.printStackTrace();
}
return returnValue;
}
}
class ToDoListCollectionImpl implements ToDoListCollection {
private HashMap lists = new HashMap();
public void add(ToDoList list) {
if (!lists.containsKey(list.getListName())) {
lists.put(list.getListName(), list);
}
}
public void remove(ToDoList list) {
if (lists.containsKey(list.getListName())) {
lists.remove(list.getListName());
}
}
public int getNumberOfItems() {
return lists.size();
}
public Iterator getIterator() {
return lists.values().iterator();
}
public String toString() {
return getClass().toString();
}
}
class DataCreator {
private static final String DEFAULT_FILE = "data.ser";
public static void main(String[] args) {
String fileName;
if (args.length == 1) {
fileName = args[0];
} else {
fileName = DEFAULT_FILE;
}
serialize(fileName);
}
public static void serialize(String fileName) {
try {
serializeToFile(createData(), fileName);
} catch (IOException exc) {
exc.printStackTrace();
}
}
private static Serializable createData() {
ToDoListCollection data = new ToDoListCollectionImpl();
ToDoList listOne = new ToDoListImpl();
ToDoList listTwo = new ToDoListImpl();
ToDoList listThree = new ToDoListImpl();
listOne.setListName("Daily Routine");
listTwo.setListName("Programmer hair washing procedure");
listThree.setListName("Reading List");
listOne.add("Get up (harder some days than others)");
listOne.add("Brew cuppa Java");
listOne.add("Read JVM Times");
listTwo.add("Lather");
listTwo.add("Rinse");
listTwo.add("Repeat");
listTwo.add("(eventually throw a TooMuchHairConditioner exception)");
listThree.add("The complete annotated aphorisms of Duke");
listThree.add("How green was my Java");
listThree.add("URL, sweet URL");
data.add(listOne);
data.add(listTwo);
data.add(listThree);
return data;
}
private static void serializeToFile(Serializable data, String fileName)
throws IOException {
ObjectOutputStream serOut = new ObjectOutputStream(
new FileOutputStream(fileName));
serOut.writeObject(data);
serOut.close();
}
}
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