Sort array list and using comparable

Question

With the following code I would like to setup a score object for the current player.
Change it to a string(Is it correct to say parse it to a string type)
Then add it to the arraylist.
So I can sort the array list according to the string size.
That's why I have the variables in that order.
So if 3 players have the same amount of guesses, they can be positioned on the high score list according to their gameTime.
//create score object
               Score currentScore = new Score(guessCount, gameTime, name);
               String currentScoreToString = currentScore.toString();
               //add score to arrayList
               scores.add(currentScoreToString);So the error message says " The method add(Score) in the type arrayList <Score> is not applicable for the arguments(string)"
Now, I understand that, I would like to know if there is another way to achieve what I am trying to do.
Is the string idea I am trying here possible? is it practical or should I use comparable?
I have looked at comparable, but I don't get it.
Will my Score class implement comparable. I am looking at an example with the following code.
Employee.java
public class Employee implements Comparable {
    int EmpID;
    String Ename;
    double Sal;
    static int i;
    public Employee() {
        EmpID = i++;
        Ename = "dont know";
        Sal = 0.0;
    public Employee(String ename, double sal) {
        EmpID = i++;
        Ename = ename;
        Sal = sal;
    public String toString() {
        return "EmpID " + EmpID + "\n" + "Ename " + Ename + "\n" + "Sal" + Sal;
    public int compareTo(Object o1) {
        if (this.Sal == ((Employee) o1).Sal)
            return 0;
        else if ((this.Sal) > ((Employee) o1).Sal)
            return 1;
        else
            return -1;
ComparableDemo.java
import java.util.*;
public class ComparableDemo{
    public static void main(String[] args) {
        List ts1 = new ArrayList();
        ts1.add(new Employee ("Tom",40000.00));
        ts1.add(new Employee ("Harry",20000.00));
        ts1.add(new Employee ("Maggie",50000.00));
        ts1.add(new Employee ("Chris",70000.00));
        Collections.sort(ts1);
        Iterator itr = ts1.iterator();
        while(itr.hasNext()){
            Object element = itr.next();
            System.out.println(element + "\n");
}The thing I don't understand is why it returns 0, 1 or -1(does it have to do with the positioning according to the object is being compared with?)
What if I only use currentScore in a loop which loops every time the player restarts?
//create score object
               Score currentScore = new Score(guessCount, gameTime, name);
               String currentScoreToString = currentScore.toString();
               //add score to arrayList
               scores.add(currentScoreToString);Also why there is a method compareTo, and where is it used?
Thanks in advance.
Edited by: Implode on Oct 7, 2009 9:27 AM
Edited by: Implode on Oct 7, 2009 9:28 AM

Answer 1

jverd wrote:
Implode wrote:
I have to hand in an assignment by Friday, and all I have to do still is write a method to sort the array list. Okay, if you have to write your own sort method, then the links I provided may not be that useful. They show you how to use the sort methods provided by the core API. You COULD still implement Comparable or Comparator. It would just be your sort routine calling it rather than the built-in ones.
You have two main tasks: 1) Write a method that determines which of a pair of items is "less than" the other, and 2) Figure out a procedure for sorting a list of items.
The basic idea is this: When you sort, you compare pairs of items, and swap them if they're out of order. The two main parts of sorting are: 1) The rules for determining which item is "less than" another and 2) Determining which pairs of items to compare. When you implement Comparable or create a Comparator, you're doing #1--defining the rules for what makes one object of your class "less than" another. Collections.sort() and other methods in the core API will call your compare() or compareTo() method on pairs of objects to produce a sorted list.
For instance, if you have a PersonName class that consists of firstName and lastName, then your rules might be, "Compare last names. If they're different, then whichever lastName is less indicates which PersonName object is less. If they're the same, then compare firstNames." This is exactly what we do in many real-life situations. And of course the "compare lastName" and "compare firstName" steps have their own rules, which are implemented by String's compareTo method, and which basically say, "compare char by char until there's a difference or one string runs out of chars."
Completely independent of the rules for comparing two items is the algorithm for which items get compared and possibly swapped. So, if you have 10 Whatsits (W1 through W10) in a row, and you're asked to sort them, you might do something like this:
Compare the current W1 to each of W2 through W10 (call the current one being compared Wn). If any of them are less than W1, swap that Wn with W1 and continue on, comparing the new W1 to W(n+1) (that is, swap them, and then compare the new first item to the next one after where you just swapped.)
Once we reach the end of the list, the item in position 1 is the "smallest".
Now repeat the process, comparing W2 to W3 through W10, then W3 to W4 through W10, etc. After N steps, the first N positions have the correct Whatsit.
Do you see how the comparison rules are totally independent of the algorithm we use to determine which items to compare? You can define one set of comparison rules ("which item is less?") for Whatsits, another for Strings, another for Integers, and use the same sorting algorithm on any of those types of items, as long as you use the appropriate comparison rules.Thanks ;)
massive help
I understand that now, but I am clueless on how to implement it.
Edited by: Implode on Oct 7, 2009 10:56 AM