What you are doing may be the simplest way, provided your stream stays sequential—otherwise you will have to put a call to sequential() before forEach. [later edit: the reason the call to sequential() is necessary is that the code as it stands (forEach(targetLongList::add)) would be racy if the stream was parallel. Even then, it will … Read more
I find that if you’re familiar with SQL syntax, using the LINQ query syntax is much clearer, more natural, and makes it easier to spot errors: var id = 1; var query = from post in database.Posts join meta in database.Post_Metas on post.ID equals meta.Post_ID where post.ID == id select new { Post = post, … Read more
I recently did a very similar thing to make a type safe OnPropertyChanged method. Here’s a method that’ll return the PropertyInfo object for the expression. It throws an exception if the expression is not a property. public PropertyInfo GetPropertyInfo<TSource, TProperty>( TSource source, Expression<Func<TSource, TProperty>> propertyLambda) { Type type = typeof(TSource); MemberExpression member = propertyLambda.Body as … Read more
You’ll need to do one of the following. If it’s your code, then define your own functional interface that declares the checked exception: @FunctionalInterface public interface CheckedFunction<T, R> { R apply(T t) throws IOException; } and use it: void foo (CheckedFunction f) { … } Otherwise, wrap Integer myMethod(String s) in a method that doesn’t … Read more
Mine would be this in c# 3.0 🙂 var type = typeof(IMyInterface); var types = AppDomain.CurrentDomain.GetAssemblies() .SelectMany(s => s.GetTypes()) .Where(p => type.IsAssignableFrom(p)); Basically, the least amount of iterations will always be: loop assemblies loop types see if implemented.
IEnumerable<Customer> filteredList = originalList .GroupBy(customer => customer.CustomerId) .Select(group => group.First());
Lambda comes from the Lambda Calculus and refers to anonymous functions in programming. Why is this cool? It allows you to write quick throw away functions without naming them. It also provides a nice way to write closures. With that power you can do things like this. Python def adder(x): return lambda y: x + … Read more
A lambda is just an anonymous function – a function defined with no name. In some languages, such as Scheme, they are equivalent to named functions. In fact, the function definition is re-written as binding a lambda to a variable internally. In other languages, like Python, there are some (rather needless) distinctions between them, but … Read more
Are you talking about lambda expressions? Like lambda x: x**2 + 2*x – 5 Those things are actually quite useful. Python supports a style of programming called functional programming where you can pass functions to other functions to do stuff. Example: mult3 = filter(lambda x: x % 3 == 0, [1, 2, 3, 4, 5, … Read more
Based on Collectors documentation it’s as simple as: Map<String, Choice> result = choices.stream().collect(Collectors.toMap(Choice::getName, Function.identity()));