Developer FAQs

Generic list type with question mark

I am having trouble interpreting/understanding the generic type of a Java List:How is the generic type ? extends Command called, like is there a name for it? What exactly is this type? Is it a Command object? Or does this mean that it only accepts classes extending Command? What is...

06月28日发表评论

Delete characters from a column 'n' characters after the given condition in R

I want to delete everything in this column 3 characters after '18'I want my output to look likeI have tried the following code.

06月28日发表评论

Clojure/FP: apply functions to each argument to an operator

Let's say I have several vectorsand that I would like to see if the names of the first elements are equal.

06月28日发表评论

Cannot assign to 'state' because it is a constant or a read-only property

When I do a search on this issue, I can only find questions that modify this.state directly somewhere in a method body instead of using this.setState(). My problem is that I want to set a starting state in the constructor as follows:

06月28日发表评论

Does structured binding work with std::vector?

Is it possible to use structured binding with vectors?E.g.Above code unfortunately doesn't work (under GCC), but maybe there's a different way (with structured binding) that allows to assign the first three values of a vector to three variables.

06月28日发表评论

Searching a value using for-loop and

The question is this:Given a non-empty array of integers, every element appears twice except for one. Find that single one.

06月28日发表评论

Spring @Autowired behavior different in tests than components

Are the rules/behaviors around @Autowired different when writing tests? It seems that with a test, you can autowire to a concrete type, but if you try the same thing inside a @Component it will fail. This is a contrived example, but it's something I ran into and am just trying...

06月28日发表评论

Generic list type with question mark

Delete characters from a column 'n' characters after the given condition in R

Clojure/FP: apply functions to each argument to an operator

Cannot assign to 'state' because it is a constant or a read-only property

Does structured binding work with std::vector?

Searching a value using for-loop and

Spring @Autowired behavior different in tests than components

Converting constructor with multiple arguments

Sorting according to clockwise point coordinates

ReasonML vs Elm [on hold]