Truncate a LinkedList

[Weijun Wang]

In my case, I am planning to do an expunge when there are more old 
entries than new entries (or plus a constant), so the "head" and "tail" 
are likely of the same size.

I'll think about creating my own LinkedList. It will be nice to just 
"break" at one link.

Thanks
Max


On 2/19/13 8:36 PM, Peter Levart wrote:
> On 02/19/2013 01:24 PM, Peter Levart wrote:
>> On 02/19/2013 11:38 AM, Daniel Fuchs wrote:
>>> On 2/19/13 11:27 AM, Weijun Wang wrote:
>>>> Hi All
>>>>
>>>> I'm using LinkedList to maintain a history and the elements are ordered
>>>> by their timestamps. Every now and then I would "expunge" the list,
>>>> that
>>>> is to say, iterating through the list and when an element is old enough
>>>> all elements after (and including) it will be removed. Currently I'm
>>>> removing them one by one.
>>>>
>>>> Is there a way to truncate the list using a single method?
>>>>
>>>> Thanks
>>>> Max
>>>
>>> Hi Max,
>>>
>>> You could try to use AbstractList.subList(...)
>>>
>>> <http://docs.oracle.com/javase/6/docs/api/java/util/AbstractList.html#subList%28int,%20int%29>
>>>
>>>
>>> Quoting from the doc:
>>>
>>>> For example, the following idiom removes a range of elements from a
>>>> list:
>>>>
>>>>       list.subList(from, to).clear();
>>>>
>> Hi Daniel,
>>
>> That's not terribly efficient. It does the list.removeRange(from, to)
>> which iterates the list again from the beginning to "from" followed by
>> iterating elements further to "to" while removing elements one-by-one.
>> That's worse than Weijun's original algorithm which iterates the
>> elements from 1st to "from" only once.
>>
>> I would make my own linked structure for that task, but if you want to
>> stick with LinkedList, your expunging algorithm could "copy" the
>> elements, from the 1st to the one that is the last to be kept, into a
>> new LinkedList and then just exchange the old list with the new...
> Hi Weijun,
>
> The above would be efficient if the remaining "head" is small compared
> to the discarded "tail". If it's the other way around, you could iterate
> the LinkedList from the end backwards and remove the elements along the
> way until you reach the one you want to keep...
>
>>
>> Regards, Peter
>>
>>>
>>> -- daniel
>>>
>>>
>>
>