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| Description html markup shown to student | <i>Booksite web exercise 4.3.2</i> Write a class <tt>CircularQuote</tt> that mimics the <tt>Quote</tt> class, but uses a circularly-linked list insteadof a null-terminated linked list. Its API will be:<pre>public CircularQuote() // constructor - create an empty quotepublic void addWord(String w) // add the word w to the end of the quotepublic String toString() // string representation of the quotepublic int count() // number of words in the quotepublic String circularGetKth(int k) // the kth word in the quote (k=1 is first // word. loops around if needed)</pre>This exercise will give you practice with <tt>do {} while ()</tt> loops.One such example loop, in the <tt>toString()</tt> method, is already completed for you.Use it again in the constructor and in <tt>count()</tt>. |
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| Template / Reference solution | public class CircularQuote { // the first card in the circular linked list private Card start; // helper linked-list data type private class Card { private String word; private Card next; private Card(String word) { this.word = word; this.next = null; } } // constructor - create an empty quote public CircularQuote() { \[ start = null; ]\ // no card intitially } // add the word w to the end of the quote public void addWord(String w) { Card newCard = \[new Card(w);]\ // degenerate case for empty quote, w is the first word if (\[start == null]\) { \[start = newCard;]\ // save the card with the new word start.next = start; // make it circular } // otherwise, traverse list until card points to last word else { // find the current last word Card card = start; do { \[card = card.next;]\ } while (\[card.next != start]\); // insert new word\[ newCard.next = start; card.next = newCard;]\ } } // string representation of the entire quote public String toString(){ String result = ""; if (start == null) // special case return result; Card card = start; do { result = result + card.word + " "; // build string card = card.next; // traverse list } while (card != start); return result; // note! using a plain while loop would normally require separate // logic for the 1-node and the (>1)-node case } // number of words in the quote public int count() {\[ // empty quote if (start == null) return 0; Card card = start; int total = 0; do { total++; card = card.next; } while (card != start); return total;]\ } // the kth word in the quote (where k = 1 is the first word) public String circularGetKth(int k) { Card card = start; for (int j = 1; j < k; j++) { card = card.next; } return card.word; } // test client public static void main(String[] args) { CircularQuote q = new CircularQuote(); StdOut.println(q.count() + ": " + q); q.addWord("A"); StdOut.println(q.count() + ": " + q); q.addWord("rose"); StdOut.println(q.count() + ": " + q); StdOut.println("Second word: " + q.circularGetKth(2)); // rose q.addWord("is"); StdOut.println(q.count() + ": " + q); StdOut.println("Tenth word: " + q.circularGetKth(10)); // A q.addWord("a"); StdOut.println(q.count() + ": " + q); StdOut.println("Seventh word: " + q.circularGetKth(7)); // is q.addWord("rose."); StdOut.println(q.count() + ": " + q); StdOut.println("First word: " + q.circularGetKth(1)); // A }} |
| Java test suite See manual | testMain(); |
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