[q] how to understand the 'order' of a list?

Question

hi,everyone
there's a test program:
import java.util.*;
public class testList
void test()
LinkedList ll= new LinkedList();
ll.add("3");
ll.add("1");
ll.add("2");
ll.add("5");
ListIterator li = ll.listIterator();
while (li.hasNext())
System.out.println(li.next());
public static void main(String[] args)
testList tl = new testList();
tl.test();
As we know, order is the most important feature of a List.
But this program's result is " 3 1 2 5 " which is not a sorted list!
How we understand the phrase 'order' ?
And , is there any method in Collection which can sort the elements in one collection (list or set)?
thanx a lot!

Answer 1

As we know, order is the most important feature of a
List. Yes, and it preserves the order you have used to put elements in the List. :)
But this program's result is " 3 1 2 5 " which is not
a sorted list!Well, what order to you actually like? "1 2 3 5"? Why not "5 3 2 1"? And for more complicated objects "natural" order may be even less obvious. And never forget that List may contain objects that belong to different classes - for example Integer, String and Date - how they are to be ordered? (Of course, such usage is not recommended).
How we understand the phrase 'order' ?
And , is there any method in Collection which can
sort the elements in one collection (list or set)?There are sort-methods in java.util.Collections class.