Why is my ArrayList not sorted?

[Tabula Rasa]

I am trying to use the compareTo method from one class, and sort the data from a file in an ArrayList, but when the program runs, the ArrayList is not sorted.
The data in the file is:

Siena,Catherine,4.0,AppliedMath
Gateau,Jean,3.5,AppliedComputing
Jones,Jill,3.0,AppliedMath
Jones,Jack,2.5AppliedComputing

The names must be sorted alphabetically according to last name, then first name, so that it prints this:

Gateau,Jean,3.5,AppliedComputing
Jones,Jack,2.5AppliedComputing
Jones,Jill,3.0,AppliedMath
Siena,Catherine,4.0,AppliedMath


My compareTo method from the AppliedStudent class:

public int compareTo(Object n)
{
AppliedStudent s = (AppliedStudent)n;
int num = lastname.compareTo(s.getLast());
return (num != 0 ? num : firstname.compareTo(s.getFirst()));
}

public String getLast()
{
return lastname;
}

public String getFirst()
{
return firstname;
}




my main class:


import javax.swing.JFrame;
import java.io.FileNotFoundException;
import java.io.File;
import java.io.PrintWriter;
import java.util.*;





public class StudentViewer
{
public static void main(String[] args) throws FileNotFoundException

{


File inputFile;
//File outputFile;

if (args.length >= 1)

{
inputFile = new File(args[0]);
//outputFile = new File(args[1]);
Scanner in = new Scanner(inputFile);

ArrayList<AppliedStudent> names = new ArrayList<AppliedStudent>();

while(in.hasNext() && in.hasNextDouble())
{
String line = in.next();
Scanner lineScanner = new Scanner(line);
lineScanner.useDelimiter("\\s*,\\s*");

String lastname = lineScanner.next();
String firstname = lineScanner.next();
double gpa = lineScanner.nextDouble();
String major = lineScanner.next();

names.add(new AppliedStudent(lastname, firstname, gpa, major));
}

Collections.sort(names);

System.out.println(names);



}
else
throw new FileNotFoundException("File Not Found");

JFrame frame = new StudentFrame(inputFile);
frame.setTitle("Applied MNS Students");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS E);
frame.setVisible(true);



}
}

[Fortu]

Please, as the first thing you do on these forums, wrap your code in
"(code)"
and
"(/code)" (using brackets "[" and "]" instead of using parenthesis) blocks of text, so your code can be read easier. It'll look like this:

Your code here.

[Junky]

1. Your code won't compile

while(in.hasNext() && in.hasNextDouble())

2. That will never be true for your data. It is asking if there is something on the next line and is it a double. Since the first token on each line is a String it will return false.

[ozzyman]

Have a look at this sample for a neat way of sorting arraylist objects:

        Person p = new Person("Bruce", "Willis");
        Person p1  = new Person("Tom", "Hanks");
        Person p2 = new Person("Nicolas","Cage");
        Person p3 = new Person("John","Travolta");
 
        ArrayList list = new ArrayList();
        list.add(p);
        list.add(p1);
        list.add(p2);
        list.add(p3);
 
        Collections.sort(list, new Comparator(){
 
            public int compare(Object o1, Object o2) {
                Person p1 = (Person) o1;
                Person p2 = (Person) o2;
               return p1.getFirstName().compareToIgnoreCase(p2.getFirstName());
            }
 
        });
 
        System.out.println(list);

Sorting an ArrayList of objects. | Some Java, JEE and WebSphere stuffs

[Tabula Rasa]

Thanks. My code works just fine on Netbeans at home, but when I get to school and try to run it, it doesn't work, even on Netbeans. The school computers have the latest JDK so I have no clue what the issue is.

[r035198x]

Explain it doesn't work.
What errors do you get? Are you providing the files and the right paths on that school computer?

[Junky]

My code works just fine on Netbeans at home, but when I get to school and try to run it, it doesn't work, even on Netbeans.

I find that very hard to believe.

[Tabula Rasa]

Explain it doesn't work.
What errors do you get? Are you providing the files and the right paths on that school computer?

My program is supposed to read any file the user puts in and sort the data according to last name, then first name.
The file I am testing is in the same directory as my program.

In my AppliedStudent class, my compareTo method is:

public int compareTo(Object n)
    {
       AppliedStudent s = (AppliedStudent)n;
       int num = lastname.compareTo(s.getLast());
       return (num != 0 ? num : firstname.compareTo(s.getFirst()));
    }

In my StudentViewer class, when I have

while(in.hasNext())

This occurs: http://i404.photobucket.com/albums/p...z/javapic2.jpg

When I include

while (in.hasNext() && in.hasNextDouble())

This occurs: http://i404.photobucket.com/albums/p...z/javapic1.jpg

...but the data is not sorted.

[ozzyman]

you never set the Results box in your frame thats why its empty?

EDIT:

so it looks like you got it working with the new while loop but you need to show us the StudentFrame class so we can find out why the results aren't displaying

[Tabula Rasa]

you never set the Results box in your frame thats why its empty?

EDIT:

so it looks like you got it working with the new while loop but you need to show us the StudentFrame class so we can find out why the results aren't displaying

I did not clarify before that right now, I'm simply trying to get the data sorted and I'm letting the data print out in the console window. The problem is, the data is not sorted.

However, when I process the same code in Netbeans, the ArrayList is sorted.

http://i404.photobucket.com/albums/p...z/javapic3.jpg

[Tabula Rasa]

Well I transferred all my code from Netbeans to notepad, and now the ArrayList is sorted.

:)