Question

Write a class that maintains the scores for a game application. Implement the addition and removal function to update the database. The gamescore.txt contains player’ name and score data record fields separated by comma. For Removal function, uses the name field to select record to remove the game score record.

Use the List.java, LList.java, Dlink.java, GameEntry.java and gamescore.txt found below

Read gamescore.txt to initialize the Linked list in sorted order by score.

Provide Remove and Add function for user to update the sorted linked list.

Display “Name exist” when add an exist name to the list.

Display “Name does not exist” when remove a name not on the list.

List.java File:

/** Source code example for "A Practical Introduction to Data

Structures and Algorithm Analysis, 3rd Edition (Java)"

by Clifford A. Shaffer

Copyright 2008-2011 by Clifford A. Shaffer

*/

/** List ADT */

public interface List<E>

{

/**

* Remove all contents from the list, so it is once again empty. Client is

* responsible for reclaiming storage used by the list elements.

*/

public void clear();

/**

* Insert an element at the current location. The client must ensure that

* the list's capacity is not exceeded.

*

* @param item

* The element to be inserted.

*/

public void insert(E item);

/**

* Append an element at the end of the list. The client must ensure that

* the list's capacity is not exceeded.

*

* @param item

* The element to be appended.

*/

public void append(E item);

/**

* Remove and return the current element.

*

* @return The element that was removed.

*/

public E remove();

/** Set the current position to the start of the list */

public void moveToStart();

/** Set the current position to the end of the list */

public void moveToEnd();

/**

* Move the current position one step left. No change if already at

* beginning.

*/

public void prev();

/**

* Move the current position one step right. No change if already at end.

*/

public void next();

/** @return The number of elements in the list. */

public int length();

/** @return The position of the current element. */

public int currPos();

/**

* Set current position.

*

* @param pos

* The position to make current.

*/

public void moveToPos(int pos);

/** @return The current element. */

public E getValue();

}

LList.java File:

/**

* Source code example for "A Practical Introduction to Data Structures and

* Algorithm Analysis, 3rd Edition (Java)" by Clifford A. Shaffer Copyright

* 2008-2011 by Clifford A. Shaffer

*/

// Doubly linked list implementation

class LList<E> implements List<E>

{

private DLink<E> head; // Pointer to list header

private DLink<E> tail; // Pointer to last element in list

protected DLink<E> curr; // Pointer ahead of current element

int cnt; // Size of list

// Constructors

LList(int size)

{

this();

} // Ignore size

LList()

{

curr = head = new DLink<E>(null, null); // Create header node

tail = new DLink<E>(head, null);

head.setNext(tail);

cnt = 0;

}

public void clear()

{ // Remove all elements from list

head.setNext(null); // Drop access to rest of links

curr = head = new DLink<E>(null, null); // Create header node

tail = new DLink<E>(head, null);

head.setNext(tail);

cnt = 0;

}

public void moveToStart() // Set curr at list start

{

curr = head;

}

public void moveToEnd() // Set curr at list end

{

curr = tail.prev();

}

/** Insert "it" at current position */

public void insert(E it)

{

curr.setNext(new DLink<E>(it, curr, curr.next()));

curr.next().next().setPrev(curr.next());

cnt++;

}

/** Append "it" to list */

public void append(E it)

{

tail.setPrev(new DLink<E>(it, tail.prev(), tail));

tail.prev().prev().setNext(tail.prev());

cnt++;

}

/** Remove and return current element */

public E remove()

{

if (curr.next() == tail)

return null; // Nothing to remove

E it = curr.next().element(); // Remember value

curr.next().next().setPrev(curr);

curr.setNext(curr.next().next()); // Remove from list

cnt--; // Decrement the count

return it; // Return value removed

}

/** Move curr one step left; no change if at front */

public void prev()

{

if (curr != head) // Can't back up from list head

curr = curr.prev();

}

// Move curr one step right; no change if at end

public void next()

{

if (curr != tail.prev())

curr = curr.next();

}

public int length()

{

return cnt;

}

// Return the position of the current element

public int currPos()

{

DLink<E> temp = head;

int i;

for (i = 0; curr != temp; i++)

temp = temp.next();

return i;

}

// Move down list to "pos" position

public void moveToPos(int pos)

{

assert (pos >= 0) && (pos <= cnt) : "Position out of range";

curr = head;

for (int i = 0; i < pos; i++)

curr = curr.next();

}

public E getValue()

{

// Return current element

if (curr.next() == tail)

return null;

return curr.next().element();

}

// reverseList() method that reverses the LList

public void reverseList()

{

LList<E> revList = new LList<E>();

curr = tail.prev();

while (curr != head)

{

revList.append(curr.element());

curr = curr.prev();

}

head.setNext(revList.head.next());

}

// Extra stuff not printed in the book.

/**

* Generate a human-readable representation of this list's contents that

* looks something like this: < 1 2 3 | 4 5 6 >. The vertical bar

* represents the current location of the fence. This method uses

* toString() on the individual elements.

*

* @return The string representation of this list

*/

public String toString()

{

// Save the current position of the list

int oldPos = currPos();

int length = length();

StringBuffer out = new StringBuffer((length() + 1) * 4);

moveToStart();

out.append("< ");

for (int i = 0; i < oldPos; i++)

{

if (getValue() != null)

{

out.append(getValue());

out.append(" ");

}

next();

}

out.append("| ");

for (int i = oldPos; i < length; i++)

{

out.append(getValue());

out.append(" ");

next();

}

out.append(">");

moveToPos(oldPos); // Reset the fence to its original position

return out.toString();

}

}

DLink.java File:

/** Source code example for "A Practical Introduction to Data

Structures and Algorithm Analysis, 3rd Edition (Java)"

by Clifford A. Shaffer

Copyright 2008-2011 by Clifford A. Shaffer

*/

/** Doubly linked list node */

class DLink<E>

{

private E element; // Value for this node

private DLink<E> next; // Pointer to next node in list

private DLink<E> prev; // Pointer to previous node

/** Constructors */

DLink(E it, DLink<E> p, DLink<E> n)

{

element = it;

prev = p;

next = n;

}

DLink(DLink<E> p, DLink<E> n)

{

prev = p;

next = n;

}

/** Get and set methods for the data members */

DLink<E> next()

{

return next;

}

DLink<E> setNext(DLink<E> nextval)

{

return next = nextval;

}

DLink<E> prev()

{

return prev;

}

DLink<E> setPrev(DLink<E> prevval)

{

return prev = prevval;

}

E element()

{

return element;

}

E setElement(E it)

{

return element = it;

}

}

GameEntry.java File:

public class GameEntry {
protected String name;
protected int score;

public GameEntry(String n, int s) {
name = n;
score = s;
}

public String getName() {return name;}

public int getScore() {return score;}

public String toString() {
return "("+name+","+score+")";
}

}

gamescore.txt File:

Mike,1105
Rob,750
Paul,720
Anna,660
Rose,590
Jack,510

Answer 1

PROGRAM CODE:

GameSimulator.java

package list;

import java.io.File;

import java.io.FileNotFoundException;

import java.util.Scanner;

public class GameSimulator {

public static void main(String[] args) {

Scanner filereader;

try {

filereader = new Scanner(new File("gamescore.txt"));

GameApplication application = new GameApplication(20);

while(filereader.hasNextLine())

{

String next = filereader.next();
int index = next.indexOf(",");
String tokens[] = new String[2];
tokens[0] = next.substring(0, index);
tokens[1] = next.substring(index+1, next.length());
GameEntry entry = new GameEntry(tokens[0], Integer.parseInt(tokens[1]));

application.add(entry);

}

System.out.println("After adding from file:");

application.print();
String option = "Y";
while(option.charAt(0)=='Y' || option.charAt(0) == 'y')
{
   Scanner keyboard = new Scanner(System.in);
   System.out.print("1. Add\n2. Remove\nEnter your choice: ");
   int choice = Integer.parseInt(keyboard.nextLine());
   String name;
   int score;
   if(choice == 1)
   {
       System.out.print("Enter the name: ");
       name = keyboard.nextLine();
       System.out.print("Enter the score: ");
       score = Integer.parseInt(keyboard.nextLine());
       GameEntry entry = new GameEntry(name, score);
       application.add(entry);
       application.print();
   }
   else if(choice == 2)
   {
       System.out.print("Enter the name: ");
       name = keyboard.nextLine();
       application.remove(name);
       application.print();
   }
   else
       System.out.println("Invalid choice");
   System.out.print("Try Again: (Y/N): ");
   option = keyboard.next();
}

} catch (FileNotFoundException e) {

System.out.println("The mentioned file is not found.");
System.exit(0);
}

  

}

}

GameApplication.java

package list;

public class GameApplication {

   LList<GameEntry> entries;

  

   public GameApplication(int size) {

   entries = new LList<GameEntry>(size);

   }

  

   private boolean checkDuplicates(String name)

   {

   boolean isPresent = false;

   for(int i=0; i<entries.length(); i++)

   {

   entries.moveToPos(i);

   if(entries.getValue().getName().equalsIgnoreCase(name))
   {
   isPresent = true;
   break;
   }
   }
   return isPresent;

   }

  

   public void add(GameEntry entry)

   {

  

   if(checkDuplicates(entry.getName()))

   {

   System.out.println("Name exist");

   return;

   }

   if(entries.length()==0)

   {

   entries.insert(entry);

   }

  

   else

   {

   entries.moveToStart();

   int counter = 0;

   while(entries.getValue() != null)

   {

   counter++;

   if(entries.getValue().getScore()>entry.getScore())

   {

   entries.insert(entry);

   break;

   }

   else if(counter==entries.length())

   {

   entries.append(entry);

   break;

   }

   else entries.next();

  

   }

   }

   }

  

   public void remove(String name)

   {

   //checking if the name exits or not
   if(!checkDuplicates(name))

   {

   System.out.println("Name does not exist");

   return;

   }

   for(int i=0; i<entries.length(); i++)

   {

   entries.moveToPos(i); //moving to the position one after the ther to check for the element and then remove it

   if(entries.getValue().getName().equals(name))

   {

   entries.remove();

   }

   }

   }

  

   // Only for debugging purpose - printing the whole list
   public void print()

   {

   System.out.println(entries);

   }

   }

OUTPUT:

After adding from file:
< | (Jack,510) (Rose,590) (Anna,660) (Paul,720) (Rob,750) (Mike,1105) >
1. Add
2. Remove
Enter your choice: 1
Enter the name: Jack
Enter the score: 320
Name exist
< | (Jack,510) (Rose,590) (Anna,660) (Paul,720) (Rob,750) (Mike,1105) >
Try Again: (Y/N): Y
1. Add
2. Remove
Enter your choice: 1
Enter the name: Mila
Enter the score: 320
< | (Mila,320) (Jack,510) (Rose,590) (Anna,660) (Paul,720) (Rob,750) (Mike,1105) >
Try Again: (Y/N): Y
1. Add
2. Remove
Enter your choice: 2
Enter the name: Anna
< (Mila,320) (Jack,510) (Rose,590) (Paul,720) (Rob,750) | (Mike,1105) >
Try Again: (Y/N): N