This is a typical late binding issue (see common gotchas): when the functions (being lambda/anonymous has nothing to do with it) are called, they access the current value of item, which is the last one from the loop. Try lambda x=item: x.data in your loop instead. This works since default arguments are bound to a … Read more
Overload resolution works only for functions that exist in a common scope. This means that the second implementation fails to find the second overload because you don’t import function call operators from overload<Frest…> into overload<F0, Frest…>. However, a non-capturing lambda type defines a conversion operator to a function pointer with the same signature as the … Read more
Short answer, you can’t. @FunctionalInterfaces cannot be used to “override” methods from Object. You can implement Formattable however, with a virtual extension method. Note: code below is UNTESTED: @FunctionalInterface public interface ToStringInterface extends Formattable { String asString(); @Override default void formatTo(Formatter formatter, int flags, int width, int precision) { formatter.format(“%s”, this); // Or maybe even … Read more
The result of a lambda expression is not a function; it is a function object. That is, it is a class type that has an operator() overload on it. So this: auto f = []<typename T>( T t ) {}; Is equivalent to this: struct unnamed { template<typename T> void operator()(T t) {} }; auto … Read more
When grouping a Stream with Collectors.groupingBy, you can specify a reduction operation on the values with a custom Collector. Here, we need to use Collectors.mapping, which takes a function (what the mapping is) and a collector (how to collect the mapped values). In this case the mapping is Person::getName, i.e. a method reference that returns … Read more
This is a modified closure See: similar questions like Access to Modified Closure To work around the issue you have to store a copy of the variable inside the scope of the for loop: foreach(AClass i in AClassCollection) { AClass anotherI= i; listOfLambdaFunctions.AddLast( () => { PrintLine(anotherI.name); } ); }
The LAMBDA expression (lambda …) is considered to be a lambda expression only in certain places, like the function form or as the head of a function call. Lambda expressions are not evaluated. (function ; special operator FUNCTION (lambda () ‘foobar)) ; <- this is a lambda expression ( ; a function call (lambda (foo) … Read more
Let’s go to the Java Language Specification on names and their scopes The scope of a formal parameter of a method (§8.4.1), constructor (§8.8.1), or lambda expression (§15.27) is the entire body of the method, constructor, or lambda expression. The scope of a local variable declaration in a block (§14.4) is the rest of the … Read more
This has more to do with lambdas than threading. A lambda captures the reference to a variable, not the variable’s value. This means that when you try to use i in your code, its value will be whatever was stored in i last. To avoid this, you should copy the variable’s value to a local … Read more
First of all… yes its a good way of doing it, it’s clean, small form and easy to read & understand… the caveat of course is “Unless you later want to unsubscribe”. I believe Jon Skeet pointed out before that “the specification explicitly doesn’t guarantee the behaviour either way when it comes to equivalence of … Read more