Download Ex-Collection-Iterator

Ex-Collections and Iterators
DictionaryTest.java
Collection Interface
import java.awt.HeadlessException;
import java.io.FileNotFoundException;
You will run this program four times,
performing experiments on four classes
that implement the Collection
interface.
import javax.swing.JOptionPane;
public class DictionaryTest {
public static void main(String[] args) {
try {
String fileName = JOptionPane.showInputDialog("Dictionary: ");
Dictionary dictTest = new Dictionary(fileName);
// The following code tests the behaviour of the Dictionary object
dictTest.loadDictionary();
JOptionPane.showMessageDialog(null, "Loading finished. Click OK to display first 100 words . . .");
dictTest.display(100);
JOptionPane.showMessageDialog(null, "Display finished. Click OK to begin searching process . . .");
dictTest.searchAllWords();
On each run, uncomment one of the
four classes. Gather timing and size
information for each class and fill in the
blanks on this page.
Use Main.txt for your timing. It’s a text
file that contains nearly 80,000 Englishlanguage words.
} catch (HeadlessException e) { // can be generated by JOptionPane.showInputDialog()
e.printStackTrace();
} catch (FileNotFoundException e) {
System.out.println("File not found.");
}
}
}
Dictionary.java
import java.io.File;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.Scanner;
import javax.swing.JOptionPane;
ArrayList
Load Time: ____________ Search Time:____________
Number of Words Loaded: ______________________
public class Dictionary {
(You’ll need to uncomment and add the import.)
private String fileName;
private Collection<String> collectionWords; // The collection type is not defined here; it will be created elsewhere.
LinkedList
Load Time: ____________ Search Time:____________
/** Constructor establishes the association with a disk-based file, so that all tests are performed on the same set of data. */
public Dictionary(String fileName) { this.fileName = fileName; }
Number of Words Loaded: ______________________
/**
* Uses the predefined filename to open a file and populate the collection sent by reference to this method.
* @throws FileNotFoundException
(You’ll need to uncomment and add the import.)
*/
public void loadDictionary() throws FileNotFoundException {
Load Time: ____________ Search Time:____________
// TODO Run the program four times. Each time, capture a different Collection class in "collectionWords"
collectionWords = new ArrayList<String>();
// collectionWords = new LinkedList<String>();
Number of Words Loaded: ______________________
// collectionWords = new TreeSet<String>();
// collectionWords = new HashSet<String>();
Scanner scanInput = new Scanner(new File(fileName));
long startTime = System.currentTimeMillis();
(You’ll need to uncomment and add the import.)
while (scanInput.hasNext()) {
String sWord = scanInput.nextLine();
Load Time: ____________ Search Time:____________
collectionWords.add(sWord); // virtual method to add another word to the collection
}
Number of Words Loaded: ______________________
scanInput.close();
double elapseTime = (double) (System.currentTimeMillis() - startTime)/1000.0;
System.out.printf("Collection Type:%s loadDictionary() Word Count:%d Elapse Time:%.3f seconds\n",
collectionWords.getClass().getName(), collectionWords.size(), elapseTime);
}
TreeSet
HashSet
/**
* Iterates through every word in the collection, looking up each in the entire collection.
* @return time (in seconds) to complete the end-to-end search process.
*/
public void searchAllWords() {
System.out.print("\n\nDisplaying one dot per thousand matches");
long startTime = System.currentTimeMillis();
int numMatches = 0;
for (String s : collectionWords) {
if (collectionWords.contains(s))
++numMatches;
Note that an enhanced for loop has only 2 parts (unlike a standard for
if (numMatches%1000 == 0)
loop that has 3). The second part must be a reference to some kind of
System.out.print(".");
}
collection. The first component will be a reference-to successive objects
double elapseTime = (double) (System.currentTimeMillis() - startTime)/1000.0;
found
in theNumber
collection.
The enhanced for loop employs a hidden iterator.
System.out.printf("\nCollection Type:%s searchAllWords() Elapse
Time:%.3f
of Matches:%d\n\n",
collectionWords.getClass().getName(), elapseTime, numMatches);
}
Enhanced for Loop Employing Implicit Iterator
/**
* Iterates through the first limitOfDisplay words and displays on the console.
* @param limitOfDisplay
*/
public void display(int limitOfDisplay) {
System.out.printf("\nFirst %d words in %s, organized using %s: \n", limitOfDisplay, fileName, collectionWords.getClass().getName());
System.out.printf("Word list generated using an enhanced for-loop (implicit iterator): \n");
int wordCount = 0;
// iterate through the collection using an enhanced for loop (with an implicit iterator)
for (String s : collectionWords) {
System.out.print(s); System.out.print(" ");
if (++wordCount % 20 == 0) // newline every 20 words
Another use of an enhanced for loop.
System.out.println();
if (wordCount >= limitOfDisplay)
break;
}
Enhanced for Loop Employing Implicit Iterator
// iterate through the collection using a while loop (with an explicit iterator)
System.out.printf("\n\nSame word list generated using a while-loop (explicit iterator): \n");
wordCount = 0;
Iterator<String> iter = collectionWords.iterator();
while (iter.hasNext()) {
String s = iter.next();
System.out.print(s); System.out.print(" ");
This is an ordinary while loop. An Iterator object is explicitly retrieved from
if (++wordCount % 20 == 0) // newline every 20 words
the Collection (one of ArrayList, LinkedList, TreeSet or HashSet). The
System.out.println();
Iterator object knows if there are more items in the Collection and how to
if (wordCount >= limitOfDisplay)
break;
move from one to the next.
}
Ordinary while Loop with Explicit Iterator
}
}
Reference-to-Object Layout
Exercise Marking Guide: Full Marks: 2
Choose one of the following Collection
classes: TreeSet, LinkedList and HashSet.
Sketch a memory map showing the
organization of memory after the 15 words
are loaded from Small.txt.
① Reasonable attempt, but some issues.
Note: Your two memory map choices must
be something other than an ArrayList.
Name: ___________________
② Essentially correct, and shown by end of lab period.
③ (Bonus) Essentially correct, and shown before (or at) the start of
the lab period.