Infinite loop while using iterator

Question

Set key1 = map.keySet();
Iterator it1 = key1.iterator();
int cnt=0;
while (it1.hasNext()) {
  cnt++;
}

What are the chances that this code will result

Answer 1

Basically itl.hasNext() always return a boolean value based on the availability of next value to process in the collection. Say pointer is at some position x, hasNext() returns true if there exists some element next to position x, i mean x+1 element exists,

So you must use itl.next(), which returns the current element in the collection and moves the pointer ahead by 1. so according to our previous example, next() returns current object a position x, and moves the pointer to next poiton.

However to get the number of elements from a collection you could use

 collection_object.size()

Answer 2

Actually it is resulting in infinite loop. My doubt is it is because I am not taking it1.next(); , is it true?

Yes, this is true.

However, you can find the count of a collection much easier:

int cnt = map.size();

Answer 3

The problem is, that you don't call it1.next() in the loop, so it1.hasNext() is always true. In other words, you never move to the next item.

BTW, you don't need iterator for what you want to archieve, try

int cnt=map.size();

Answer 4

Yes. Until you don't call it1.next() it will never move on to next item. Beause it1.next() will return the object which you have added in the list/set.