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Commit add6448

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Chap 21, Ex: 14,15.
1 parent 20da60e commit add6448

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4 files changed

+146
-12
lines changed

4 files changed

+146
-12
lines changed

‎ch_07/Exercise07_02.java‎

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@@ -13,6 +13,7 @@ public static void main(String[] args) {
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Scanner input = new Scanner(System.in);
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System.out.println("Enter ten space-separated integers: ");
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int[] arr = new int[10];
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for (int i = 0; i < 10; i++) {

‎ch_08/Exercise08_36.java‎

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@@ -39,7 +39,6 @@ public static void main(String[] args) {
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char[][] chars = new char[numRows][numRows];
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int upperBoundChar = minChar + numRows - 1; //Upper Bound for the range from 'A' -> ('A' + userInput)
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System.out.println("\nEnter " + numRows + " rows of capital letters separated by spaces: ");
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try {
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for (int r = 0; r < chars.length; r++) {
@@ -54,7 +53,7 @@ public static void main(String[] args) {
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} catch (Exception e) {
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e.printStackTrace();
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System.out.println(e.getLocalizedMessage());
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notALSq();
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System.out.println("The input array is not a Latin Square.");
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System.exit(0);
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}
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@@ -78,7 +77,7 @@ public static void main(String[] args) {
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} else if (rowTracker.size() != 0) {
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if (rowTracker.contains(charValue)) {
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notALSq();
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System.out.println("The input array is not a Latin Square.");
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result = false;
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break ROW;
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}
@@ -99,7 +98,7 @@ public static void main(String[] args) {
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if (colTracker.size() > 0) {
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if (colTracker.contains(value)) {
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notALSq();
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System.out.println("The input array is not a Latin Square.");
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break OUTER;
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}
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}
@@ -109,12 +108,4 @@ public static void main(String[] args) {
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}
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in.close();
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}
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static void notALSq() {
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System.out.println("The input array is not a Latin Square.");
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}
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static void aLsq() {
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System.out.println("The input array is a Latin Square.");
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}
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}

‎ch_21/Exercise21_14.java‎

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@@ -0,0 +1,99 @@
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package ch_21;
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import java.net.URL;
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import java.util.*;
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/**
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* *21.14 (Web crawler) Rewrite Listing 12.18, WebCrawler.java,
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* to improve the performance by using appropriate
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* new data structures for listOfPendingURLs and listofTraversedURLs.
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*/
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public class Exercise21_14 {
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public static void main(String[] args) {
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java.util.Scanner input = new java.util.Scanner(System.in);
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System.out.print("Enter a URL: ");
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String url = input.nextLine();
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crawler(url); // Traverse the Web from the a starting url
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}
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public static void crawler(String startingURL) {
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/* Exercise 21.14
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...improve the performance by using appropriate new data structures for listOfPendingURLs and
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listofTraversedURLs.
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*/
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TreeSet<CrawlUrl> listOfPendingURLs = new TreeSet<>();
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HashSet<CrawlUrl> listOfTraversedURLs = new HashSet<>();
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listOfPendingURLs.add(new CrawlUrl(startingURL));
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while (!listOfPendingURLs.isEmpty() &&
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listOfTraversedURLs.size() <= 100) {
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CrawlUrl crawUrl = listOfPendingURLs.first();
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listOfPendingURLs.remove(crawUrl);
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if (!listOfTraversedURLs.contains(crawUrl)) {
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listOfTraversedURLs.add(crawUrl);
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System.out.println("Crawl: " + crawUrl);
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for (CrawlUrl crawlUrl : getSubURLs(crawUrl.getUrlString())) {
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if (!listOfTraversedURLs.contains(crawlUrl))
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listOfPendingURLs.add(crawlUrl);
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}
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}
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}
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}
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public static Set<CrawlUrl> getSubURLs(String urlString) {
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Set<CrawlUrl> set = new HashSet<>(); // Exercise 21.14
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try {
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URL url = new URL(urlString);
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Scanner input = new Scanner(url.openStream());
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int current = 0;
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while (input.hasNext()) {
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String line = input.nextLine();
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current = line.indexOf("http:", current);
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while (current > 0) {
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int endIndex = line.indexOf("\"", current);
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if (endIndex > 0) { // Ensure that a correct URL is found
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set.add(new CrawlUrl(line.substring(current, endIndex)));
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current = line.indexOf("http:", endIndex);
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} else
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current = -1;
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}
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}
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} catch (Exception ex) {
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System.out.println("Error: " + ex.getMessage());
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}
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return set;
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}
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}
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/**
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* Implements Comparable for default sorting when used in a TreeSet
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*/
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class CrawlUrl implements Comparable<CrawlUrl> {
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private String urlString;
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public CrawlUrl(String urlString) {
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this.urlString = urlString;
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}
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@Override
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public int compareTo(CrawlUrl that) {
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// Implement to sort by the length of the url
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return Integer.compare(this.urlString.length(), that.urlString.length());
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}
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public String getUrlString() {
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return urlString;
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}
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public CrawlUrl setUrlString(String urlString) {
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this.urlString = urlString;
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return this;
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}
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@Override
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public String toString() {
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return "CrawlUrl{" +
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"urlString='" + urlString + '\'' +
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'}';
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}
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}

‎ch_21/Exercise21_15.java‎

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@@ -0,0 +1,43 @@
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package ch_21;
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import java.util.HashSet;
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import java.util.Scanner;
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import java.util.Set;
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/**
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* *21.15 (Addition quiz) Rewrite Programming Exercise 11.16 to store the answers in a
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* set rather than a list.
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* <p>
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* {@linkplain ch_11.Exercise11_16}
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*/
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public class Exercise21_15 {
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public static void main(String[] args) {
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Set<Integer> guesses = new HashSet<>();
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Scanner input = new Scanner(System.in);
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int number1 = (int) (Math.random() * 10);
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int number2 = (int) (Math.random() * 10);
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System.out.print("What is " + number1 + " + " + number2 + "? ");
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int answer = input.nextInt();
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while (answer != number1 + number2) {
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if (guesses.contains(answer)) {
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System.out.println("You've already entered " + answer);
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System.out.print("Try again. What is " + number1 + " + " + number2 + "? ");
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answer = input.nextInt();
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} else {
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guesses.add(answer);
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System.out.print("Wrong answer. Try again. What is " + number1 + " + " + number2 + "? ");
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answer = input.nextInt();
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}
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}
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input.close();
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System.out.println("You got it!");
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}
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}

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