1) There are many examples on the Internet and on StackOverflow about the particular issue with generics and varargs. Basically, it’s when you have a variable number of arguments of a type-parameter type: <T> void foo(T… args); In Java, varargs are a syntactic sugar that undergoes a simple “re-writing” at compile-time: a varargs parameter of … Read more
Varargs are useful for any method that needs to deal with an indeterminate number of objects. One good example is String.format. The format string can accept any number of parameters, so you need a mechanism to pass in any number of objects. String.format(“This is an integer: %d”, myInt); String.format(“This is an integer: %d and a … Read more
Yes, a T… is only a syntactic sugar for a T[]. JLS 8.4.1 Format parameters The last formal parameter in a list is special; it may be a variable arity parameter, indicated by an elipsis following the type. If the last formal parameter is a variable arity parameter of type T, it is considered to … Read more
To pass the ellipses on, you initialize a va_list as usual and simply pass it to your second function. You don’t use va_arg(). Specifically; void format_string(char *fmt,va_list argptr, char *formatted_string); void debug_print(int dbg_lvl, char *fmt, …) { char formatted_string[MAX_FMT_SIZE]; va_list argptr; va_start(argptr,fmt); format_string(fmt, argptr, formatted_string); va_end(argptr); fprintf(stdout, “%s”,formatted_string); }
With params you can call your method like this: addTwoEach(1, 2, 3, 4, 5); Without params, you can’t. Additionally, you can call the method with an array as a parameter in both cases: addTwoEach(new int[] { 1, 2, 3, 4, 5 }); That is, params allows you to use a shortcut when calling the method. … Read more
In C++11 you have two new options, as the Variadic arguments reference page in the Alternatives section states: Variadic templates can also be used to create functions that take variable number of arguments. They are often the better choice because they do not impose restrictions on the types of the arguments, do not perform integral … Read more
ES6 using rest parameters If you are able to use ES6 you can use: Rest Parameters function sortArgs(…args) { return args.sort(function (a, b) { return a – b; }); } document.body.innerHTML = sortArgs(12, 4, 6, 8).toString(); As you can read in the link The rest parameter syntax allows us to represent an indefinite number of … Read more
Heap pollution is a technical term. It refers to references which have a type that is not a supertype of the object they point to. List<A> listOfAs = new ArrayList<>(); List<B> listOfBs = (List<B>)(Object)listOfAs; // points to a list of As This can lead to “unexplainable” ClassCastExceptions. // if the heap never gets polluted, this … Read more
Add dots after the second slice: //—————————vvv append([]int{1,2}, []int{3,4}…) This is just like any other variadic function. func foo(is …int) { for i := 0; i < len(is); i++ { fmt.Println(is[i]) } } func main() { foo([]int{9,8,7,6,5}…) }
It means that zero or more String objects (or a single array of them) may be passed as the argument(s) for that method. See the “Arbitrary Number of Arguments” section here: http://java.sun.com/docs/books/tutorial/java/javaOO/arguments.html#varargs In your example, you could call it as any of the following: myMethod(); // Likely useless, but possible myMethod(“one”, “two”, “three”); myMethod(“solo”); myMethod(new … Read more