sorting a vector

[jeff willis]

hi,
I need to sort a vector. Anyone have any good ideas on how to implement this?

I'm kind of suprised that the JAVA core doesn't supply a sorting method.

[Susanta Chatterjee]

Yes, it does.

 public static void sort(List list) 

method of java.util.Collections class and java.util.Vector implements java.util.List interface.

Regards,
Susanta

[marc weber]

Vector now implements the List interface, so you should be able to use the sort capabilities in java.util.Collections. If your elements implement Comparable, then you can use sort(List). Otherwise, you can use sort(List, Comparator).

[jeff willis]

I must be doing something wrong.

My vector is a simple list of names.
I populate it in a loop with this statement:

 
vctAcct.add( new String (acctName) );
 

Then I sort it like this:

 
Collections.sort(vctAcct);
 

Then I use it to create a JTable. The elements are not sorted in the table.

Have I missed something?

[Dirk Schreckmann]

These days, it's recommended to not use Vector. Use a different type of list, like ArrayList, instead.

If you're curious for the reasoning behind this, I'd recommend a quick search on this forum for "vector arraylist" in the subject. (Note that the search page link is at the top right of this page.) Also, you might like to read the JavaWorld Java Q&A on the subject.

Even if yours is a learning exercise, you might as well learn to use the preferred APIs, while doing it.

Concerning this line of code:

vctAcct.add( new String (acctName) );

Is acctName a String? If so, why are you creating a new String with a String? Are you familiar with what the difference between the following two lines of code are?

String string1 = "myString";
String string2 = new String("myString");

On the issue of sorting, forgetting about the JTable for a moment, have you tried just iterating through the collection, after sorting it, and simply printing it out to the console to see if it got sorted correctly?

[jeff willis]

You're on to something there.

I printed out the vector before the sort and after the sort.

It DID appear sorted when the output went to stdout!

I need to examine how I am implementing my table.

...now about the populating of the Vector...

I used the new String() because my string variable was declared inside the loop like this:

 
    for (int i = 0; i < nl.getLength(); i++)
    {
       // get an account record...
      Node node = nl.item(i);
 
      // get the name from the account
      String acctName = readElement( node, "NAME");
 
      if ((acctName != null) && (acctName != "") )
        vctAcct.add( new String (acctName) );
    } 

Are you saying that this is not necessary?

[Susanta Chatterjee]

Trigger the fireTableUpdate event on tableModel interface to update the GUI.

[Dirk Schreckmann]

I used the new String() because my string variable was declared inside the loop
...
Are you saying that this is not necessary?

Yes. I'm also saying that using the String(String) constructor has a particular side effect that you might not be aware of, and you might not be concerned with. Take a look at the String class documentation for a brief explanation of that side effect. This gets to the topic of the String pool, which you might want to start a new thread for, if you have questions about it. I'd also recommend trying a quick search on this forum and on google for the subject.

If you end up with questions about working with a JTable, I'd recommend moseying on over to the Swing / AWT / SWT / JFace forum, and starting a new thread.
[ September 23, 2004: Message edited by: Dirk Schreckmann ]