Tuesday, April 06, 2004



8:11:23 PM    comment []
 


I wanted to remove a range of items from a list using the List.subList method. I tried the following: 
	// al is defined previously as ArrayList al = new ArrayList();
        List l = al.subList(20,50);
        al.removeAll(l);

That got me the java.util.ConcurrentModificationException

The documentation says that a subList is dependent on the List that it is sublisting from. So, while a sublist is open, it is manipulating the parent list and seems to have a lock on it.   Instead, you can create a brand new ArrayList and fill it with the subList, thus freeing up the sublist so that a future call can modify the original List: 

	ArrayList sl = new ArrayList(al.subList(10,40));
    	al.removeAll(sl);

So why does

 List = myList.subList(10,30);

get you a different animal than

ArrayList temp = new ArrayList(myList.subList(10,30)); ??

because in the first snippet, I haven't instantiated a new object, I just created a reference to an existing object.   In the second snippet, I created a brand new object.  That's what the word "new" gets me.


6:06:45 PM    comment []
 


For some reason, the ever so humble blog reduces my blood pressure whenever I read it.  I think it is the pictures of  the birds at her bird feeder.  Or maybe the picture of boots at the top.    Discovered it via true life
5:52:18 PM    comment []
 


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