Does a java for-each loop guarantee that the elements will be presented in order if invoked on a list? In my tests it does seem to, but I can't seem to find this explicitly mentioned in any documentation
List<Integer> myList;// [1,2,3,4] for (Integer i : myList) { System.out.println(i.intValue()); } #output 1,2,3,4
Yes. The foreach loop will iterate through the list in the order provided by the iterator() method.
3) The enhanced for loop can only iterate in incremental order. we cannot configure it to go in decrement.
The forEach method was introduced in Java 8. It provides programmers a new, concise way of iterating over a collection. The forEach method performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.
Yes. The foreach loop will iterate through the list in the order provided by the iterator()
method. See the documentation for the Iterable interface.
If you look at the Javadoc for List you can see that a list is an "ordered collection" and that the iterator()
method returns an iterator that iterates "in proper sequence".
The foreach
loop will use the iterator built into the Collection
, so the order you get results in will depend whether or not the Collection
maintains some kind of order to the elements.
So, if you're looping over an ArrayList
, you'll get items in the order they were inserted (assuming you didn't go on to sort the ArrayList). If you're looping over a HashSet
, all bets are off, since HashSets don't maintain any ordering.
If you need to guarantee an order to the elements in the Collection, define a Comparator
that establishes that order and use Collections.sort(Collection<T>, Comparator<? super T>)
.
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