[SOLVED] In detail, how does the 'for each' loop work in Java?

In detail, how does the 'for each' loop work in Java?

Consider:

List<String> someList = new ArrayList<>();
// add "monkey", "donkey", "skeleton key" to someList

for (String item : someList) {
    System.out.println(item);
}

What would the equivalent for loop look like without using the for each syntax?

_{People new to Java commonly encounter issues when trying to modify the original data using the new style foreach loop. Use Why doesn't assigning to the iteration variable in a foreach loop change the underlying data? to close duplicates about that common problem. Note that other languages with analogous constructs generally have the same issue; for example, see Why doesn't modifying the iteration variable affect subsequent iterations? for the same issue in Python.}

Solution

for (Iterator<String> i = someIterable.iterator(); i.hasNext();) {
    String item = i.next();
    System.out.println(item);
}

Note that if you need to use i.remove(); in your loop, or access the actual iterator in some way, you cannot use the for ( : ) idiom, since the actual iterator is merely inferred.

As was noted by Denis Bueno, this code works for any object that implements the Iterable interface.

If the right-hand side of the for (:) idiom is an array rather than an Iterable object, the internal code uses an int index counter and checks against array.length instead. See the Java Language Specification.

for (int i = 0; i < someArray.length; i++) {
    String item = someArray[i];
    System.out.println(item);
}