collections – Page 19

Automapper : mapping issue with inheritance and abstract base class on collections with Entity Framework 4 Proxy Pocos

August 1, 2023 by Tarik

This answer comes ‘a bit’ late as I’ve just faced the same issue with EF4 POCO proxies. I solved it using a custom converter that calls Mapper.DynamicMap<TDestination>(object source) to invoke the runtime type conversion, rather than the .Include<TOtherSource, TOtherDestinatio>(). It works fine for me. In your case you would define the following converter: class PaymentConverter … Read more

Java’s Collections.shuffle is doing what?

August 1, 2023 by Tarik

Yes, you can look at the code; it basically does a Fisher-Yates shuffle. Here it is (thanks OpenJDK, and yay for open source :-P): public static void shuffle(List<?> list, Random rnd) { int size = list.size(); if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) { for (int i=size; i>1; i–) swap(list, i-1, rnd.nextInt(i)); } else … Read more

Why does ArrayList have “implements List”? [duplicate]

August 1, 2023 by Tarik

Yes. It could’ve been omitted. But thus it is immediately visible that it is a List. Otherwise an extra click through the code / documentation would be required. I think that’s the reason – clarity. And to add what Joeri Hendrickx commented – it is for the purpose of showing that ArrayList implements List. AbstractList … Read more

Converting ArrayList of Characters to a String?

July 31, 2023 by Tarik

You can iterate through the list and create the string. String getStringRepresentation(ArrayList<Character> list) { StringBuilder builder = new StringBuilder(list.size()); for(Character ch: list) { builder.append(ch); } return builder.toString(); } Setting the capacity of the StringBuilder to the list size is an important optimization. If you don’t do this, some of the append calls may trigger an … Read more

Flattening an Iterable in Guava

July 31, 2023 by Tarik

The Iterables.concat method satisfies that requirement: public static <T> Iterable<T> concat(Iterable<? extends Iterable<? extends T>> inputs)

Java merge 2 collections in O(1)

July 30, 2023 by Tarik

You can create a concatenated Iterable view in O(1) using one of Guava’s Iterables.concat methods: Iterable<T> combined = Iterables.concat(list1, list2); This will allow you to iterate over all the elements of both lists as one object without copying any elements.

How can I convert Scala Map to Java Map with scala.Float to java.Float k/v conversion

July 30, 2023 by Tarik

The solution linked to by @pagoda_5b works: Scala convert List[Int] to a java.util.List[java.lang.Integer] scala> import collection.JavaConversions._ import collection.JavaConversions._ scala> val m = mapAsJavaMap(Map(1 -> 2.1f)).asInstanceOf[java.util.Map[java.lang.Integer, java.lang.Float]] m: java.util.Map[Integer,Float] = {1=2.1} scala> m.get(1).getClass res2: Class[_ <: Float] = class java.lang.Float

Hibernate Validation of Collections of Primitives

July 29, 2023 by Tarik

Neither JSR-303 nor Hibernate Validator has any ready-made constraint that can validate each elements of Collection. One possible solution to address this issue is to create a custom @ValidCollection constraint and corresponding validator implementation ValidCollectionValidator. To validate each element of collection we need an instance of Validator inside ValidCollectionValidator; and to get such instance we … Read more