COmparator with strings that contains numbers, * and #

[celia05es]

Hello,
I have been trying to solve my problem since this morning but I cannot do it!!!
Please, help me.
I have an array. Each element can contain digits, "*" or/and "#". I would like to sort the array using comparator... but I can't seem to find the correct algorithm.

COuld you help me?

Thanks
ELisabeth

 

[Diancecht]

Ok, let's clarify some points:

1.- You can only convert to numbers Strings that contain just numbers.

2.- By default, Strings are sorted alphabetically.

3.- If you want to sort Strings that represents numbers, a way is converting them to numbers. That won't work for mixed Strings (letters + digits)

4.- If you want a differente sorting algoritmh than the default one, you have to implement it via the Comparable interface or any other mechanism.

Cheers,

Dian

 

[celia05es]

THat's the problem I am having. I have tried to implement the sort wia the Comparable interface but it is not working correctly. COuld you help me with it?

 

[Diancecht]

Didn't the code I give you work?

 

[celia05es]

No, because the strings can contain letters and numbers.
So, I need to have them sorted correctly.
For instance:
100
1001
900
user1
user2
user11
etc.

 

[Diancecht]

Ok, define your WHOLE problem with ALL requirements, not just pieces of it, and I'll try to give you some help.

For example:

"100" < "user1" ?
"100!" < "100a" ?
"1001" < "900" ?

Cheers,

Dian

 

[celia05es]

Fair enough!
Here is what I think would do:
- The strings will only contain letters and numbers.
- The number order should be respected:
100<200<900<1001
- The alphabetical order should be respected too:
foo<user<user1< user10
For instance:
100
100a
100ab
100u
1a300
200
201a
...
usu
usu1
....

Thank you

 

[sedj]

What operating system are you on ?

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[celia05es]

uname -a" gives: "SunOS out 5.7 Generic_106541-12 sun4u sparc SUNW,Ultra-5_10"

 

[sedj]

Right,

the easiest way is to use the native "sort" program.

Create a file with your to_be_sorted stuff in it ("abc.txt"), and then run this code :

public class Test {
 	public static void main(String args[]) throws Exception {
		String file = "abc.txt";
		String fileOut = "abc_sorted.txt";
		Process p = Runtime.getRuntime().exec("sort " +file +" -o " +fileOut);
		p.waitFor();
       }
}

Ta Da !



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[celia05es]

That is a good idea but now how do I include this in my code!!
I mean, I have a file.java with a lot of rutines. A lot of rutines will use this sort, so this sort has to be a routine that can be called.
I have tried to compile the code and run it but I must do something wrong because when I try to execute it (java Test)I get:
Exception in thread "main" java.lang.NoClassDefFoundError: Test

 

[sedj]

set your CLASSPATH to include your directory where the Test.class is.

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[celia05es]

How stupid of me!!!!
OK, it does exactly what I need....
Now, how can I include it in my routines?

Something else... I don't have a file but a Vector.

 

[sedj]

Well, you would have to write out the contents of the vector to a file, sort it, and then read the contents back into a vector.

You do realise this is probably a really, really inefficient and stupid way of doing it though right ?

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[celia05es]

I know that 's why I wanted to write a Comparator....
Any idea about how I could write a Comparator?

 

[jstreich]

Can you pad the numbers in the strings with zeros?
If so, the library provided comparisons will work...

0100 < 0900 < 1001 < user1 < user2 < user11

So, the order you want is
- In alpha order
- If the first char is numaric grab the whole first number and compare as an int
And you say they are only alpha numaric, but were talking about * and # ... So, which is it?

Alright how about this (in psuedo code)

if(one starts with a digit and other doesn't)
  return that the one with digit is smaller
if(first char of both are digits)
{
  get the whole first number (all chars that are digits) from both 
  if the numbers are equal 
    continue 
  else return the result
}
else
{
  compare the string, striping all numbers that may be in middle or end of string (storing them for comparison)
  if(strings w/o nums equal)
      compare the numbers you striped out
  else return the inequality
}

Why is this sorted order so important, and why are there so many numbers in all different places in the string? It seems that there should be a little more consistancy to the strings in most applications... To be honest you may want to consider writing several small/simpler comparitors and just sort using each untill the order and sub order and sub-suborder are exactly as you want...

Is al10fred < al020fred or al020fred < al10fred
10 < 020 in numbers, but asciibetical and alphabetical (by most standards) 020 < 10.

Just some food for thought

 

[Diancecht]

The list you gave is ordered alphabetically.

That can be done through java.util.Arrays.sost(String[]) method.

Cheers,

Dian

 

[celia05es]

Thank you very much for the pseudo code. I will come back to my customer and ask him about some more restrictive rules.
Thank you so much for your time....

MERRY CHRISTMAS to everyone.

Elisabeth