Mergesort referencing Comparable objects

[Joe Grimp]

Ok here is what i have to do -

I need to complete and test class SortLinkedList below which is intended to perform a mergesort on a linked list of LinearNodes referencing Comparable objects, by providing code to:

Complete the method printList which outputs the list to the output file.

Complete the recursive method countList which counts the number of items on the list

Complete the code for method LinkedMergeSort as indicated


Here is my code:

  import java.io.*;
import java.util.Scanner;
public class SortLinkedList
{
 
   static FileWriter fw;
   static BufferedWriter bw;
   static PrintWriter outFile; 
   public static void main(String[] args)throws IOException 
   {
 
   String line, name;
      Scanner fileScanner;
LinearNode list = null;
LinearNode temp;
 
int accNum, num;
double accBal;
Account1 acc;
 

      fileScanner = new Scanner (new File("accounts.dat"));
     fw = new FileWriter ("lines.out");
bw = new BufferedWriter (fw);
outFile = new PrintWriter (bw);
 
while(fileScanner.hasNext())
{
line = fileScanner.nextLine();
         Scanner lineScanner = new Scanner(line);
 
name = lineScanner.next();
accNum= lineScanner.nextInt();
accBal = lineScanner.nextDouble();
 
acc = new Account1(name, accNum, accBal);
temp = new LinearNode(acc);
temp.setNext(list);
list = temp;
}
 

 
outFile.println("Accounts List");
outFile.println("Number\tName\tBalance");
printList(list);
outFile.println("Number of Accounts  " + countList(list));
 
list = LinkedMergeSort(list);
 
outFile.println("Accounts List");
outFile.println("Number\tName\tBalance");
printList(list);
outFile.println("Number of Accounts  " + countList(list)); 
outFile.close();
}
 
public static void printList(LinearNode L)
{
[B]// how do i output the list to the file here??[/B]}
 
public static int countList(LinearNode L) 
{ 
          [B]//   how do i count the number of items on the list here
          //   using a recursive method??[/B]
}
 

 


public static LinearNode LinkedMergeSort(LinearNode L)
{
if (L.getNext()!=null)
{
LinearNode temp,tail, lowList, highList;
int mid, index;

mid = countList(L)/2;

                        [B]// I don't know what to do with the intructions
                           given below???[/B]
// get to middle of the list
// by moving temp along
 


// form lowList and highList
// making highlist reference second half 
// and unhitching the second half from the first


// Sort the lists with recursive calls
lowList = LinkedMergeSort(lowList);
highList = LinkedMergeSort(highList);


L=null;
tail = null;

// Merge lowList and highList into L
//while there are items on both lists
//compare items at start of the two lists
// make temp ref smaller and remove from its list
// put item temp refs onto end of list L
if(L==null) L=temp;
else tail.setNext(temp);
tail = temp;
tail.setNext(null);
// connect remainder of lowList or highList to end of L

}
return L;
}

}


 

  

Thanks for any help anyone can give me. Joe.

[Ulf Dittmer]

This sounds like an assignment that you should be doing, so any help provided here will be general in nature.

public static void printList(LinearNode L)
{
// how do i output the list to the file here??}

public static int countList(LinearNode L)
{
// how do i count the number of items on the list here
// using a recursive method??
}

The answer to this depends on what class LinearNode is and does, about which we know nothing. Have you checked its API to see if there may be helpful methods in it?