iterable

I am a beginner and I cannot understand the real effect of the Iterable interface. Besides what Jeremy said, its main benefit is that it has its own bit of syntactic sugar: the enhanced for-loop . If you have, say, an Iterable<String> , you can do: for (String str : myIterable) { ... } Nice and easy, isn't it? All the dirty work of creating the Iterator<String> , checking if it hasNext() , and calling str = getNext() is handled behind the scenes by the compiler. And since most collections either implement Iterable or have a view that returns one (such as Map 's keySet() or values() ), this

UPDATE: An idea to make built-in strings non-iterable was proposed on python.org in 2006 . My question differs in that I'm trying to only suppress this features once in a while; still this whole thread is quite relevant. Here are the critical comments by Guido who implemented non-iterable str on a trial basis: [...] I implemented this (it was really simple to do) but then found I had to fix tons of places that iterate over strings. For example: The sre parser and compiler use things like set("0123456789") and also iterate over the characters of the input regexp to parse it. difflib has an API

In Java 5 and above you have the foreach loop, which works magically on anything that implements Iterable : for (Object o : list) { doStuff(o); } However, Enumerable still does not implement Iterable , meaning that to iterate over an Enumeration you must do the following: for(; e.hasMoreElements() ;) { doStuff(e.nextElement()); } Does anyone know if there is a reason why Enumeration still does not implement Iterable ? Edit: As a clarification, I'm not talking about the language concept of an enum , I'm talking a Java-specific class in the Java API called ' Enumeration '. Enumeration hasn't

I read Why is Java's Iterator not an Iterable? and Why aren't Enumerations Iterable? , but I still don't understand why this: void foo(Iterator<X> it) { for (X x : it) { bar(x); baz(x); } } was not made possible. In other words, unless I'm missing something, the above could have been nice and valid syntactic sugar for: void foo(Iterator<X> it) { for (X x; it.hasNext();) { x = it.next(); bar(x); baz(x); } } gustafc but I still don't understand why this [...] was not made possible. I can see several reasons: Iterator s are not reusable, so a for/each would consume the iterator - not incorrect

I have an Array of primitives, for example for int, int[] foo. It might be a small sized one, or not. int foo[] = {1,2,3,4,5,6,7,8,9,0}; What is the best way to create an Iterable<Integer> from it? Iterable<Integer> fooBar = convert(foo); Notes: Please do not answer using loops (unless you can give a good explanation on how the compiler do something smart about them?) Also note that int a[] = {1,2,3}; List<Integer> l = Arrays.asList(a); Will not even compile Type mismatch: cannot convert from List<int[]> to List<Integer> Also check Why is an array not assignable to Iterable? before answering.

This questions stems from PEP 448 -- Additional Unpacking Generalizations and is present in Python 3.5 as far as I'm aware (and not back-ported to 2.x ). Specifically, in the section Disadvantages , the following is noted: Whilst *elements, = iterable causes elements to be a list , elements = *iterable , causes elements to be a tuple . The reason for this may confuse people unfamiliar with the construct. Which does indeed hold, for iterable = [1, 2, 3, 4] , the first case yields a list : >>> *elements, = iterable >>> elements [1, 2, 3, 4] While for the second case a tuple is created: >>>