For-each vs Iterator. Which will be the better option

Question

Consider the following scenario.

List<String> list = new ArrayList<>(); 

Now I added the String values for this list.

I used following ways to go each and every element in the list.

Option one- use for-each

for (String i : list) {         System.out.println(i);     }  

Option two- use Iterator

Iterator it=list.iterator(); while (it.hasNext()){    System.out.println(it.next()); } 

I just want to know is there any performance advantage if I use for-each instead of Iterator. And also is it a bad practice to use Iterator now a days in Java?

Answer 1

for-each is syntactic sugar for using iterators (approach 2).

You might need to use iterators if you need to modify collection in your loop. First approach will throw exception.

for (String i : list) {     System.out.println(i);     list.remove(i); // throws exception }   Iterator it=list.iterator(); while (it.hasNext()){     System.out.println(it.next());     it.remove(); // valid here } 

Answer 2

The difference is largely syntactic sugar except that an Iterator can remove items from the Collection it is iterating. Technically, enhanced for loops allow you to loop over anything that's Iterable, which at a minimum includes both Collections and arrays.

Don't worry about performance differences. Such micro-optimization is an irrelevant distraction. If you need to remove items as you go, use an Iterator. Otherwise for loops tend to be used more just because they're more readable ie:

for (String s : stringList) { ... } 

vs:

for (Iterator<String> iter = stringList.iterator(); iter.hasNext(); ) {   String s = iter.next();   ... }