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

Question

Consider the following scenario.

List list = new ArrayList<>();

Now I added the String values for this li

Answer 1

Simple answers: No and no.

Internally the for-each loop creates an Iterator to iterate through the collection.

The advantage of using the Iterator explicitly is that you can access the Iterators method.

Answer 2

Here is simple code snippet to check the performance of For-each vs Iterator vs for for the traversal of ArrayList<String>, performed on Java version 8.

        long MAX = 2000000;

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

        for (long i = 0; i < MAX; i++) {

            list.add("" + i);
        }

        /**
         * Checking with for each iteration.
         */
        long A = System.currentTimeMillis();

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

        long B = System.currentTimeMillis();
        System.out.println(B - A + "ms");

        /**
         * Checking with Iterator method
         */

        Iterator<String> iterator = list.iterator();
        while (iterator.hasNext()) {
            iterator.next();
            // System.out.println(iterator.next());
        }

        long C = System.currentTimeMillis();
        System.out.println(C - B + "ms");

        /**
         * Checking with normal iteration.
         */
        for (int i = 0; i < MAX; i++) {
            list.get((int) (i % (MAX - i)));
            // System.out.println(list.get(i));
        }

        long D = System.currentTimeMillis();
        System.out.println(D - C + "ms");

Average Output values:

19ms
9ms
27ms

Result Analysis: Iterator (9ms) < For-each (19ms) < For (27ms)

Here Iterator has the best performance and For has the least performance. However For-each performance lies somewhere in between.