Regarding concurrent modification Exception [closed]

Answer 1

A ConcurrentModificationException can be thrown in a single thread environment. It is used whenever an object is modified in a context where it shouldn't, not necessarily in another thread.

Example:

public class CME {
    public static void main(String...args) {
        HashSet coll = new HashSet();
        coll.add(1);
        coll.add(2);
        coll.add(3);

        for(Integer i : coll) {
            coll.remove(i); // Throws ConcurrentModificationException
        }
    }
}