compareTo & sort [Java]

[gumOnShoe]

So I created a Row class which just holds onto an ArrayList of Strings.

Each Row has a set number of unique identifiers. That is if there are 30 Rows in a "Document" then indices 0, 1, and 2 could be unique (primary keys), so that when I sort the document I want it sorted by the first three strings in each array list, 0 being the most important, then 1 and 2 in that order.

Java's built in merge sort is stable, so it seems if I could sort by 2 and then 1 and then 0, I'd be golden, but Java's built in sort uses the compareTo method to sort a given list. [See Collection in the JavaDocs]

Strings also have a built in compareTo method, but returning the value of one string doesn't cut it as that value may be compared to a different index later on by Collection.sort(). Similarly, I can't simply concatenate the strings because if String A = "ab" and String B = "a", then String C = "a" and String D "ba" would result in Row { A, B } == Row { C, D }.

I'm curios as to what you think the solution to this is... I'm sure its something simple I haven't thought of... also speed is essential. (I could be dealing with a million rows easily)

[Jon-86]

Are you trying to sort alphabetically? Word length? Word frequency? The way I read it you have explained what your doing and not the problem your trying to solve. Unless I read it wrong. Let me know and I should be able to get back to you the morra. Need to sleep now.

Unless you or someone else figures it out before then, sounds like an interesting problem!

[fourthfrench]

I'm a little confused by your question, but is this what you are looking to do?

import java.util.ArrayList;
import java.util.Collections;

class Row implements Comparable<Row>
{
	ArrayList<String> al;
	public Row(ArrayList<String> al){this.al = al;}
	public int compareTo(Row o)
	{
		for(int i=0; i<3; i++)
			if(!al.get(i).equals(o.al.get(i)))
				return al.get(i).compareTo(o.al.get(i));
		return 0;
	}
	public String toString(){return al.toString();}
}
public class Sort 
{
	public static void main(String[] args)
	{
		ArrayList<String> one = new ArrayList<String>();
		ArrayList<String> two = new ArrayList<String>();
		one.add("ab");
		one.add("a");
		two.add("a");
		two.add("ba");
		Row a = new Row(one);
		Row b = new Row(two);
		ArrayList<Row> rows = new ArrayList<Row>();
		rows.add(a);
		rows.add(b);
		Collections.sort(rows);
		System.out.println(rows);
		//[[a, ba], [ab, a]]
	}
}

~fourthfrench