Question: Write a class that maintains the top ten scores for a game application, implementing the add and remove methods of Section 3.1.1, but using a
Write a class that maintains the top ten scores for a game application, implementing the add and remove methods of Section 3.1.1, but using a singly linked list instead of an array in Java. Using the example code:
Scored Board:
public class Scoreboard {
private int numEntries = 0; // number of actual entries
private GameEntry[] board; // array of game entries (names & scores)
/** Constructs an empty scoreboard with the given capacity for storing entries. */
public Scoreboard(int capacity) {
board = new GameEntry[capacity];
}
/** Attempt to add a new score to the collection (if it is high enough) */
public void add(GameEntry e) {
int newScore = e.getScore();
// is the new entry e really a high score?
if (numEntries < board.length || newScore > board[numEntries-1].getScore()) {
if (numEntries < board.length) // no score drops from the board
numEntries++; // so overall number increases
// shift any lower scores rightward to make room for the new entry
int j = numEntries - 1;
while (j > 0 && board[j-1].getScore() < newScore) {
board[j] = board[j-1]; // shift entry from j-1 to j
j--; // and decrement j
}
board[j] = e; // when done, add new entry
}
}
/** Remove and return the high score at index i. */
public GameEntry remove(int i) throws IndexOutOfBoundsException {
if (i < 0 || i >= numEntries)
throw new IndexOutOfBoundsException("Invalid index: " + i);
GameEntry temp = board[i]; // save the object to be removed
for (int j = i; j < numEntries - 1; j++) // count up from i (not down)
board[j] = board[j+1]; // move one cell to the left
board[numEntries -1 ] = null; // null out the old last score
numEntries--;
return temp; // return the removed object
}
/** Returns a string representation of the high scores list. */
public String toString() {
StringBuilder sb = new StringBuilder("[");
for (int j = 0; j < numEntries; j++) {
if (j > 0)
sb.append(", "); // separate entries by commas
sb.append(board[j]);
}
sb.append("]");
return sb.toString();
}
public static void main(String[] args) {
// The main method
Scoreboard highscores = new Scoreboard(5);
String[] names = {"Rob", "Mike", "Rose", "Jill", "Jack", "Anna", "Paul", "Bob"};
int[] scores = {750, 1105, 590, 740, 510, 660, 720, 400};
for (int i=0; i < names.length; i++) {
GameEntry gE = new GameEntry(names[i], scores[i]);
System.out.println("Adding " + gE);
highscores.add(gE);
System.out.println(" Scoreboard: " + highscores);
}
System.out.println("Removing score at index " + 3);
highscores.remove(3);
System.out.println(highscores);
System.out.println("Removing score at index " + 0);
highscores.remove(0);
System.out.println(highscores);
System.out.println("Removing score at index " + 1);
highscores.remove(1);
System.out.println(highscores);
System.out.println("Removing score at index " + 1);
highscores.remove(1);
System.out.println(highscores);
System.out.println("Removing score at index " + 0);
highscores.remove(0);
System.out.println(highscores);
}
}
Scored Board SLL
public class ScoreboardSLL {
private int numEntries = 0; // number of actual entries
private int maxEntries = 10;
private SinglyLinkedList
/** Constructs an empty scoreboard with the given capacity for storing entries. */
public ScoreboardSLL(int capacity) {
board = new SinglyLinkedList<>();
maxEntries = capacity;
}
/** Attempt to add a new score to the collection (if it is high enough) */
public void add(GameEntry e) {
int newScore = e.getScore();
SinglyLinkedList
// is the new entry e really a high score?
if (numEntries < maxEntries || newScore > board.last().getScore()) {
if (numEntries < maxEntries) // no score drops from the board
{
numEntries++;
if (board.isEmpty())
board.addFirst(e);
//list is not maxed
else if(board.first().getScore() < newScore)
//add first
board.addFirst(e);
else if (board.last().getScore() > newScore)
//add last
board.addLast(e);
else
{
//add in between
while ( newScore < board.first().getScore())
{
tempList.addLast(board.removeFirst());
}
tempList.addLast(e);
tempList.concatenate(board);
board = tempList;
}
}
else
{
// Add in between by moving to tempList all entries from board except the last one
// First move to tempList all the entries with a score higher than newScore using tempList.addLast() method
// Then, add the entry "e" to tempList using addLast() method
// Finally, add to tempList the rest of board entries except the last one
// To keep track when the last entries is reached, there needs to be a counter variable
// The counter variable is incremented with each addLast()
// To exclude the last entry from board the counter variable must be < maxEntries
// --------- type your code here ----------------
}
}
}
/** Remove and return the high score at index i. */
public GameEntry remove(int i) throws IndexOutOfBoundsException {
if (i < 0 || i >= numEntries)
throw new IndexOutOfBoundsException("Invalid index: " + i);
// -------- type your code here using SinglyLinkedList instead of array ------------
/*
GameEntry temp = board[i]; // save the object to be removed
for (int j = i; j < numEntries - 1; j++) // count up from i (not down)
board[j] = board[j+1]; // move one cell to the left
board[numEntries -1 ] = null; // null out the old last score
numEntries--;
*/
return temp; // return the removed object
}
/** Returns a string representation of the high scores list. */
public String toString() {
StringBuilder sb = new StringBuilder("[");
/*for (int j = 0; j < numEntries; j++) {
if (j > 0)
sb.append(", "); // separate entries by commas
sb.append(board[j]);
}*/
sb.append(board.toString());
sb.append("]");
return sb.toString();
}
public static void main(String[] args) {
// The main method
Scoreboard_1 highscores = new Scoreboard_1(5);
String[] names = {"Rob", "Mike", "Rose", "Jill", "Jack", "Anna", "Paul", "Bob"};
int[] scores = {750, 1105, 590, 740, 510, 660, 720, 400};
for (int i=0; i < names.length; i++) {
GameEntry gE = new GameEntry(names[i], scores[i]);
System.out.println("Adding " + gE);
highscores.add(gE);
System.out.println(" Scoreboard: " + highscores);
}
/*
System.out.println("Removing score at index " + 3);
highscores.remove(3);
System.out.println(highscores);
System.out.println("Removing score at index " + 0);
highscores.remove(0);
System.out.println(highscores);
System.out.println("Removing score at index " + 1);
highscores.remove(1);
System.out.println(highscores);
System.out.println("Removing score at index " + 1);
highscores.remove(1);
System.out.println(highscores);
System.out.println("Removing score at index " + 0);
highscores.remove(0);
System.out.println(highscores);
*/
}
}
Game Entry
public class GameEntry {
private String name; // name of the person earning this score
private int score; // the score value
/** Constructs a game entry with given parameters.. */
public GameEntry(String n, int s) {
name = n;
score = s;
}
/** Returns the name field. */
public String getName() { return name; }
/** Returns the score field. */
public int getScore() { return score; }
/** Returns a string representation of this entry. */
public String toString() {
return "(" + name + ", " + score + ")";
}
}
Step by Step Solution
There are 3 Steps involved in it
Get step-by-step solutions from verified subject matter experts