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Hello
I am using add and previous method of iterators
List<objectt> list = new ArrayList<objectt>() ;
ListIterator<orderedpair> iterator = list.iterator();
iterator.add();
iterator.previous();
but I get exception after previous() .Are there any example to refer for proper usage of add alongwith previous()
Pritha
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why are you using an iterator? it's a List.
list.add(value);
should work fine.
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thanks for ur reply
yes that works fine
but how do i go to previous once an element is added.
i get an unhandled exception checkforcomodification
pritha
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Why do you step back?
ConcurrentModificationException is thrown when more than one action is taking place at the same time on the List. A read access and an (still running) asynchronous write access is probably to much at a time.
A List is not a ordered thing. You will have to sort when you want a certain lineup of values - but there are better types when you are looking for a ordered list. The question must be - do you really need a ordered list or do you just want to store values?
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thank you for a wonderful explanation
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TorstenH. wrote: A List is not a ordered thing.
Yes, it is. This is how the javadoc for java.util.List defines a List:
An ordered collection (also known as a sequence).
The fact that a List is ordered is what distinguishes it from other collection types such as a Bag (although Java does not actually have a Bag type out of the box).
I ran a little test to repeat the OP's example using ArrayList and it worked perfectly, exactly as expected, no exception thrown. So I think you are right, there is something else going on here, probably to do with threads - that's typically where you see ConcurrentModification, where one thread is reading the list and another thread is updating it.
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Right, a List might be ordered in some way - The objects are placed as they come in.
I don't consider that as a real order as that is only the time relevant order in which the List is filled. So Strings e.g. would be in there non alphabetical, numbers, dates and so would be mixed up.
To get a real order according to what you expect/want the objects to be in the list you need to sort them: Object Ordering @ Java Tutorials[^]
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You're using 'ordered' to mean 'sorted' there which is rather confusing, as a list does indeed preserve the order of items and therefore to me is indeed 'ordered' (unlike, say, a map).
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right, sort and order might be a bit mixed up.
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TorstenH. wrote: To get a real order according to what you expect/want the objects to be in the
list you need to sort them
No, I don't. I can add items to the list at any position I want. One way to do this is to use the overloaded add method, which allows me to specify the index position at which I want to add the item.
This allows me to add items to the list in any arbitrary order I want, even if it does not correspond to a natural sort order. For example, I can add numbers in the order 3, 1, 4, 1, 9 which are the digits of pi in sequence. But wait! I hear you cry, that's not right. So now I go back and add the digit 5 into my list at index 4 to make 3, 1, 4, 1, 5, 9. If I add the number at the end, it's wrong. If I sort it, it's wrong. I have to add it into the correct position to get the order I want and expect.
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and how do you determine what is missing or what you're searching for?
I guess one should sort to get the right order.
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Are you saying that the correct solution is always to add to the end of a list and then sort it? That inserting into a specific index position within a list is always wrong?
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no, that is your thought.
One has a List of complex Objects(e.g. cars)
A new Object should be added to the List. Position refers to an specified argument of the Objects (e.g. power of car).
It is easier to add the object to the end of the List and then to sort the List with a simple, fixed Comparator.
I don't know what you are coding, but I have seldom simple types in my Collections.
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It may be easier to add at the end of the list, but that doesn't mean it's more efficient. I'm guessing you've never heard of an insertion sort algorithm.
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please help me to find a good java proposal to my java final project.. still we are learning java @ university but they asked us to give the java final project proposal.. so im hopeless in finding a good project..if anyone have a good new idea plz let me knw..
thx..
F.R.Majeed
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Hi there,
I have an interview in a few hours for a new job which requires java technology.
I have some basic java knowledge and most things I found back in my .Net knowledge (Apache/Tomcat is similar to IIS, JVM is more or less CLR, etc...), but I was curious about the EJB specs. Are they like Session, Application and messaging objects in .NET ? That's what I gather from all the info on google, but I have the feeling that I'm missing a key point here. Most articles keep very vague in saying it makes the developer focus on the business logic eg.
So my question is, could you explain, in a nutshell, EJB (or other common java technologies) or point me to a good article (couldn't find one, not even wiki)
Many thanks.
V.
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Looking at some of these links[^] I don't think you have time.
Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman
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Thanks, that was idd my problem. That's why I wanted to know if there was something similar in .Net. Then I could map my .Net knowledge with this feature.
The articles are indeed lengthy and vague imho.
V.
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The interview went unexpectedly well  .
They figured that with my experience I could learn the new technologies very quickly anyway and they seemed more interested in motivation.
V.
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what is the advance java and functon...??????
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What indeed? Please think about your question before posting, as the above makes no sense. In fact you could probably type it into Google and get a reasonable answer.
Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman
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i have created one java servlet code from which i get 3 field from database table and i want to show this field on my js(java script) page in html tag like <lable>Name= and i want to show first name field from datbase infront of lable Name..
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OK, now we know what you want. What's your question?
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