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The for-each loop, added in Java 5 (also called the "enhanced for loop"), is equivalent to using a java.util.Iterator --it's syntactic sugar for the same thing. Therefore, when reading each element, one by one and in order, a for-each should always be chosen over an iterator, as it is more convenient and concise.
Jul 1, 2009 · Method #1: Iterating over entries using a For-Each loop. This is the most common method and is preferable in most cases. It should be used if you need both map keys and values in the loop. Map<Integer, Integer> map = new HashMap<Integer, Integer>(); for (Map.Entry<Integer, Integer> entry : map.entrySet()) {.
Mar 16, 2010 · 450. The easiest way to for-each every char in a String is to use toCharArray(): for (char ch: "xyz".toCharArray()) {. } This gives you the conciseness of for-each construct, but unfortunately String (which is immutable) must perform a defensive copy to generate the char[] (which is mutable), so there is some cost penalty. From the documentation:
In Java 1.8 (Java 8) this has become lot easier by using forEach method from Aggregate operations (Stream operations) that looks similar to iterators from Iterable Interface. Just copy paste below statement to your code and rename the HashMap variable from hm to your HashMap variable to print out key-value pair. HashMap<Integer,Integer> hm ...
Being somewhat new to the Java language I'm trying to familiarize myself with all the ways (or at least the non-pathological ones) that one might iterate through a list (or perhaps other collections) and the advantages or disadvantages of each. Given a List<E> list object, I know of the following ways to loop through all elements:
I use a JSON library called JSONObject (I don't mind switching if I need to).. I know how to iterate over JSONArrays, but when I parse JSON data from Facebook I don't get an array, only a JSONObject, but I need to be able to access an item via its index, such as JSONObject[0] to get the first one, and I can't figure out how to do it.
Nov 14, 2012 · It's necessary that you get each row from the container, and then each element from each row. for(int[] u: uu) is simply a for-each iteration rows, with the same principle of for(int row = 0; row < container.length; row++), and u or respectively container[row] are not elements themselves, but rows (arrays) of elements.
The official way to do this is to call map.entrySet(), which returns a set of Map.Entry, each of which contains a key and a value (entry.getKey() and entry.getValue()). In an idiosyncratic implementation, it might make some difference whether you use map.keySet(), map.entrySet() or something else.
You should be able to do it in Java by creating a custom implementation of Iterable which will return the elements in reverse order. Then, you would instantiate the wrapper (or call the method, what-have-you) which would return the Iterable implementation which reverses the element in the for each loop.
Sep 27, 2010 · @cletus: but here it isn't syntactic sugar. Generally we have rather memory vs cpu problem. I wouldn't mind if JVM optimizes access to String methods somehow, but still you call .lenght() and .charAt() for each char. –
