Problem in arraylist

[syruss kumar]

Hi all,

I have tried to iterate a list and if the object contains specific character i have to remove the object but it throws concurrentmodificationexception because iterate has been aware of what is modified.so i tried with for loop but its not working properly.

	List<String> lst=new ArrayList<String>();
		lst.add("1");
		lst.add("2");
		lst.add("2");
		lst.add("2");
		lst.add("3");
		lst.add("4");
		lst.add("5");
		
		for(int count=0;count<=lst.size();count++){
			String str=lst.get(count);
			if(str.contains("2")){
				lst.remove(count);
			}
		}

If i execute this objects in the list is not removed completely.I debugged the code the objects are swapped once its removed.


Please suggest me how to avoid concurrentmodificationexception

[Darryl Burke]

Go through the tutorial.

edit

the objects are swapped once its removed.

It should be rather obvious that if you remove, say, the second element, then the third element takes its place. To remove elements in a for loop, start at the highest numbered element and proceed toward zero.

[D. Ogranos]

Darryl Burke wrote:To remove elements in a for loop, start at the highest numbered element and proceed toward zero.

To remove objects from a list while iterating over it, using an iterator is the safer way I think. Something like:

  void mymethod() {
    List<String> lst = new ArrayList<String>();
    // fill list
    for (Iterator<String> iter = lst.iterator(); iter.hasNext(); ) {
      String currentElement = iter.next();
      if (currentElement.contains("xyz")) {
        iter.remove();
      }
    }
  }

[Rob Spoor]

Both techniques, using an Iterator or looping backwards, will solve this issue. Whichever you prefer is best -- I usually go for the Iterator.

[syruss kumar]

Thanks a lot for the suggestion its helped me to resolve the issue .