Sorting ArrayList Objects. : arraylist, sort

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12.10.2004 at 07:27AM PST, ID: 21237976

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7.0

Sorting ArrayList Objects.

Zone: Java Programming Language

Tags: arraylist, sort

Hi,

Below is the class which sorts the list of strings and integers. I passed the arguments as 115R 1125R 147C 37R 57R 37C and it shows the result as 1125R 115R 147C 37C 37R 57R. But the problem is I want the output as 37C 37R 57R 115R 147C 1125R. Can anyone help me with this. Its really important.

import java.util.*;

public class SortArrayList
{
      public static void main(String s[])
      {
            Collections col;
            List l = sort(s);

            System.out.println("\nStrings sorted List ...");
            for(int i = 0; i < s.length; i++)
            {
                  System.out.println((String)l.get(i));
            }

            int ints[] = {
                                    11, 2, -22, 401, 6
                                    };

            Integer in[] = new Integer[ints.length];
            for(int i = 0; i < in.length; i++)
            {
                  in[i] = new Integer(ints[i]);
            }

            l = sort(in);
            System.out.println("\nIntegers sorted List ...");

            for(int i = 0; i < in.length; i++)
            {
                  System.out.println((Integer)l.get(i));
            }
}

public static List sort(Object o[])
{
            ArrayList al = new ArrayList();
            for(int i = 0; i < o.length; i++)
            al.add(i, o[i]);
            List list = Collections.synchronizedList(al);
            Collections.sort(list);
            return list;
}
}

Thanks.

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Question Stats

Zone: Programming

Question Asked By: sunny08

Solution Provided By: zzynx

Participating Experts: 2

Solution Grade: A

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12.10.2004 at 07:40AM PST, ID: 12793180

Rank: Genius

zzynx:

Try replacing

Collections.sort(list);

by

Collections.sort(list, new Comparator() {

public int compare(Object o1, Object o2) {
String s1 = (String)o1;
String s2 = (String)o2;

String integer1[] = s1.split("[0-9]");
String integer2[] = s2.split("[0-9]");
String chars1[] = s1.split("[^0-9]");
String chars2[] = s2.split("[^0-9]");

Integer i1 = new Integer( Integer.parseInt(integer1[0]) );
Integer i2 = new Integer( Integer.parseInt(integer2[0]) );

if (i1.equals(i2)
return chars1[1].compareTo(chars2[1]);
else
return i1.compareTo(i2);
}
});

12.10.2004 at 07:42AM PST, ID: 12793202

Rank: Genius

zzynx:

>> Its really important.
Maybe you could have considered 500pts ;°)

12.10.2004 at 07:46AM PST, ID: 12793272

Rank: Genius

zzynx:

Wait a minute... that's not OK...

12.10.2004 at 07:50AM PST, ID: 12793319

Rank: Genius

zzynx:

Correction:

Collections.sort(list, new Comparator() {

public int compare(Object o1, Object o2) {
String s1 = (String)o1;
String s2 = (String)o2;

String integer1[] = s1.split("[^0-9]"); // <<<<< changed
String integer2[] = s2.split("[^0-9]"); // <<<<< changed
String chars1[] = s1.split("[0-9]+"); // <<<<< changed
String chars2[] = s2.split("[0-9]+"); // <<<<< changed

Integer i1 = new Integer( Integer.parseInt(integer1[0]) );
Integer i2 = new Integer( Integer.parseInt(integer2[0]) );

if (i1.equals(i2)
return chars1[1].compareTo(chars2[1]);
else
return i1.compareTo(i2);
}
});

12.10.2004 at 07:51AM PST, ID: 12793335

Rank: Genius

zzynx:

I assumed that your list contains Strings like "115R", "1125R", "147C", "37R", "57R", "37C",...

12.10.2004 at 08:17AM PST, ID: 12793640

AceMcCloud:

zzynx is 100% correct that you should use a comparator, but you might find a simpler impelementation more readable.

I'm also not a big fan of anonymous inner class (they clutter the code something awful IMO).

Something like this would work just as well:

Collections.sort(list, new SpecialComarator());

Class SpecialComparator
implements Comparator
{
public int compare(Object o1, Object o2)
{
String s1 = (String)o1;
String s2 = (String)o2;

int offset1 = findCharOffset(s1);
int offset2 = findCharOffset(s2);

int v1 = Integer.parseInt(s1.substring(0,offset1));
int v2 = Integer.parseInt(s2.substring(0,offset2));

int difference = v1 - v2;

if (difference != 0)
{
return difference;
}

return s1.substring(offset1).compareTo(s2.substring(offset2));
}

private int findCharOffset(String value)
{
integer result = 0;
while (result < value.length() && Character.isDigit(value.charAt(result))
{
result++;
}

return result;
}
}

12.10.2004 at 08:24AM PST, ID: 12793720

Rank: Genius

zzynx:

>> I'm also not a big fan of anonymous inner class
In this case I find an inner class is on it's place: It's here that you need the sorting; it's here that you find the Comparator class.
But, that's a matter of taste of course ;°)

>>...but you might find a simpler impelementation more readable.
Well, it's a matter of being/making yourself familiar with regular expressions.
In the past I also wasn't a big fan of them.
But once you discover their power...

12.10.2004 at 08:26AM PST, ID: 12793757

sunny08:

Hi zzynx,

Thank you for the quick response. I executed the code which shows the result as 1125R 115R 147C 37C 37R 57R. but I need the result as 37C 37R 57R 115R 147C 1125R. Can you help me with this.

Thanks.

12.10.2004 at 08:34AM PST, ID: 12793853

Rank: Genius

zzynx:

Are you sure?
For me it just works:

List list = new ArrayList();
list.add("1125R");
list.add("115R");
list.add("147C");
list.add("37C");
list.add("37R");
list.add("57R");
Collections.sort(list, new Comparator() {

public int compare(Object o1, Object o2) {
String s1 = (String)o1;
String s2 = (String)o2;

String integer1[] = s1.split("[^0-9]"); // <<<<< changed
String integer2[] = s2.split("[^0-9]"); // <<<<< changed
String chars1[] = s1.split("[0-9]+"); // <<<<< changed
String chars2[] = s2.split("[0-9]+"); // <<<<< changed

Integer i1 = new Integer( Integer.parseInt(integer1[0]) );
Integer i2 = new Integer( Integer.parseInt(integer2[0]) );

if (i1.equals(i2))
return chars1[1].compareTo(chars2[1]);
else
return i1.compareTo(i2);
}});
System.out.println("\nStrings sorted List ...");
for(int i = 0; i < list.size(); i++) {
System.out.println((String)list.get(i));
}

Output:
Strings sorted List ...
37C
37R
57R
115R
147C
1125R

12.10.2004 at 08:35AM PST, ID: 12793860

Rank: Genius

zzynx:

I'm going offline. Success.

12.10.2004 at 08:38AM PST, ID: 12793896

AceMcCloud:

>>>...but you might find a simpler impelementation more readable.
> Well, it's a matter of being/making yourself familiar with regular expressions.
> In the past I also wasn't a big fan of them.
> But once you discover their power...

Sure, regular expressions are powerful things and I know full well HOW to use them. I'm not conviced that they are the most appropriate solution in this case - they're TOO powerful and unnecessarily complicate an essentially simple problem.

An of course, that too is a matter of taste. I'm a card carrying member of "Do The Simplest Thing That Could Possibly Work".

Actually thinking about it more clearly, something like this would also work:

Class SpecialComparator
implements Comparator
{
public int compare(Object o1, Object o2)
{
String s1 = (String)o1;
String s2 = (String)o2;

int v1 = Integer.parseInt(s1.substring(0,s1.length() - 1));
int v2 = Integer.parseInt(s2.substring(0,s2.length() - 1));

int difference = v1 - v2;

if (difference != 0)
{
return difference;
}

return Character.getNumericValue(s1.charAt(length() - 1) -
Character.getNumericValue(s2.charAt(length() - 1);
}

12.10.2004 at 08:48AM PST, ID: 12793997

sunny08:

Hi,

I am not getting the write output. I don't think this is working, but hey thanks for the response. I appreciate that.

Thanks.

12.11.2004 at 04:08AM PST, ID: 12799372

Rank: Genius

zzynx:

>> I am not getting the write output
You mean with what I posted? Impossible. It just works for me!
It outputs:
37C
37R
57R
115R
147C
1125R

Can you show us the exact code you have for the moment? There must be something wrong with it...

12.12.2004 at 06:28PM PST, ID: 12806171

sunny08:

Hi zzynx,

Here is the exact code which I have. Please help me with this. Here is the arguments which I passed while executing 115R 1125R 147C 37R 57R 37C and I am getting the output as 1125R 115R 147C 37C 37R 57R. Below is the code:

import java.util.*;

public class SortObjects
{
      public static void main(String s[])
      {
            Collections col;
            List l = sort(s);

            System.out.println("\nStrings sorted List ...");
            for(int i = 0; i < s.length; i++)
            {
                  System.out.println((String)l.get(i));
            }

            int ints[] = {
                                    11, 2, -22, 401, 6
                                    };

            Integer in[] = new Integer[ints.length];
            for(int i = 0; i < in.length; i++)
            {
                  in[i] = new Integer(ints[i]);
            }

            l = sort(in);
            System.out.println("\nIntegers sorted List ...");

            for(int i = 0; i < in.length; i++)
            {
                  System.out.println((Integer)l.get(i));
            }
}

public static List sort(Object o[])
{
            ArrayList al = new ArrayList();
            for(int i = 0; i < o.length; i++)
            al.add(i, o[i]);
            List list = Collections.synchronizedList(al);

            Collections.sort(list, new Comparator()
            {

public int compare(Object o1, Object o2)
{

      String s1 = (String)o1;
String s2 = (String)o2;

int v1 = Integer.parseInt(s1.substring(0,s1.length() - 1));
int v2 = Integer.parseInt(s2.substring(0,s2.length() - 1));

int difference = v1 - v2;

if (difference != 0)
{
return difference;
}

return Character.getNumericValue(s1.charAt(s1.length() - 1)) -
Character.getNumericValue(s2.charAt(s1.length() -1));

}
});

            //Collections.sort(list , new SpecialComparator());

            System.out.println("\nStrings sorted List ...");

            for(int i = 0; i < list.size(); i++)
System.out.println((String)list.get(i));

            return list;
}

}

Thanks in advance.

12.12.2004 at 07:07PM PST, ID: 12806281

sunny08:

hi,

I have tried this code too.

/*
* Created on Dec 10, 2004
*
* @author z688240
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/

import java.util.*;

public class SortObjects
{
      public static void main(String s[])
      {
            Collections col;
            List l = sort(s);

            System.out.println("\nStrings sorted List ...");
            for(int i = 0; i < s.length; i++)
            {
                  System.out.println((String)l.get(i));
            }

            int ints[] = {
                                    11, 2, -22, 401, 6
                                    };

            Integer in[] = new Integer[ints.length];
            for(int i = 0; i < in.length; i++)
            {
                  in[i] = new Integer(ints[i]);
            }

            l = sort(in);
            System.out.println("\nIntegers sorted List ...");
  &nb