swith to circular list to shift easier

Question

I have a private arraylist with classes that include two longs, a float and a BigDecimal. As new data comes in I currently am removing the oldest element, shifiting all other elements over, and then adding the newest element. I think this is taking up a lot of memory uncessearly. So is there anyway to make this a circle, so I don't need to shift over elements in the array?

I'll include the relevenat parts of my code below:

private ArrayList<privStat> MyList = new ArrayList<privStat>();
public class privStat {
   long Stat1;
   long Stat2;
   float Stat3;
   BigDecimal Stat4;
}

NewStat = new privStat(//new message)
if (MyList.size() - 1 < 10) {
   MyList.add(NewStat);
} else {
   Mylist.remove(0);
   Mylist.add(NewStat);
}

Isn't linkedlist sufficient for this purpose? If I remember correctly, it has good performance for insert/delete operations. — kosa, Mar 06 '12 at 15:34

score 2 · Answer 1 · answered Mar 06 '12 at 15:35

2

Sounds like you're trying to implement a queue in Java. Read this.

Java also provides a LinkedList class which can be easily implemented as a queue. Here's an example.

answered Mar 06 '12 at 15:35

CFL_Jeff

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score 1 · Answer 2 · answered Mar 06 '12 at 15:36

1

Why not use a first-in, first-out data structure such as a Queue like LinkedList? This will allow you to add at the back of the queue, and remove from the front. Both operations will take constant time.

answered Mar 06 '12 at 15:36

smessing

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score 1 · Answer 3 · answered Mar 06 '12 at 15:44

If I understood question right, you have to see to Queue class, I think it work more efficiently behind the scenes. (http://docs.oracle.com/javase/6/docs/api/java/util/Queue.html)

Or you can use array and mod operation (but it will be a circle, not queue):

PrivStat[] privStats=new PrivStat[10]();
int i=0;

and use next code for add:

privStats[i]=newStat;
i=(++i) % 10;

swith to circular list to shift easier

3 Answers3