If you are just wandering over the collection to read all of the values, then there is no difference between using an iterator or the new for loop syntax, as the new syntax just uses the iterator underwater. If however, you mean by loop the old “c-style” loop: for(int i=0; i<list.size(); i++) { Object o … Read more
In my opinion the better choice is Guava (formerly known as Google collections): it’s more modern (has generics) it absolutely follows the Collections API requirements it’s actively maintained CacheBuilder and it’s predecessor MapMaker are just plain awesome Apache Commons Collections is a good library as well, but it has long failed to provide a generics-enabled … Read more
Assuming that those are Strings, use the convenient static method sort: Collections.sort(listOfCountryNames)
Apache commons collections 4 has a CircularFifoQueue<> which is what you are looking for. Quoting the javadoc: CircularFifoQueue is a first-in first-out queue with a fixed size that replaces its oldest element if full. import java.util.Queue; import org.apache.commons.collections4.queue.CircularFifoQueue; Queue<Integer> fifo = new CircularFifoQueue<Integer>(2); fifo.add(1); fifo.add(2); fifo.add(3); System.out.println(fifo); // Observe the result: // [2, 3] If … Read more
foreach: foreach (var money in myMoney) { Console.WriteLine(“Amount is {0} and type is {1}”, money.amount, money.type); } MSDN Link Alternatively, because it is a List<T>.. which implements an indexer method [], you can use a normal for loop as well.. although its less readble (IMO): for (var i = 0; i < myMoney.Count; i++) { … Read more
Use a Comparator like this: List<Fruit> fruits= new ArrayList<Fruit>(); Fruit fruit; for(int i = 0; i < 100; i++) { fruit = new Fruit(); fruit.setname(…); fruits.add(fruit); } // Sorting Collections.sort(fruits, new Comparator<Fruit>() { @Override public int compare(Fruit fruit2, Fruit fruit1) { return fruit1.fruitName.compareTo(fruit2.fruitName); } }); Now your fruits list is sorted based on fruitName.
I’m pretty sure the static frequency-method in Collections would come in handy here: int occurrences = Collections.frequency(animals, “bat”); That’s how I’d do it anyway. I’m pretty sure this is jdk 1.6 straight up.
The way to make this work is to iterate over the list and cast the elements. This can be done using ConvertAll: List<A> listOfA = new List<C>().ConvertAll(x => (A)x); You could also use Linq: List<A> listOfA = new List<C>().Cast<A>().ToList();
I hope you were joking about writing your own parser. 🙂 For such a simple mapping, most tools from http://json.org (section java) would work. For one of them (Jackson https://github.com/FasterXML/jackson-databind/#5-minute-tutorial-streaming-parser-generator), you’d do: Map<String,Object> result = new ObjectMapper().readValue(JSON_SOURCE, HashMap.class); (where JSON_SOURCE is a File, input stream, reader, or json content String)
Use the .clone() method on your List. It will return a shallow copy, meaning that it will contain pointers to the same objects, so you won’t have to copy the list. Then just use Collections. Ergo, Collections.reverse(list.clone()); If you are using a List and don’t have access to clone() you can use subList(): List<?> shallowCopy … Read more