variadic-functions

This will not compile: public class Methods { public static void method(Integer... i) { System.out.print("A"); } public static void method(int... i) { System.out.print("B"); } public static void main(String args[]) { method(7); } } This will compile and work: public class Methods { public static void method(Integer i) { System.out.print("A"); } public static void method(int i) { System.out.print("B"); } public static void main(String args[]) { method(7); } } First and second example are very similar. First uses varargs, second not. Why one works, second not. 7 is primitive, so second method

I have not seen the particular thing before today when working on variable length argument For e.g., There is a method named prepared statement with declaration such that 1. String prepareStatement(String... columnNames,String... values) //String... columnNames(Eclipse shows error saying The variable argument type String of the method prepareStatement must be the last parameter) 2. Another method declaration String prepareStatement(int i,String... columnNames,String... values) //still the same result as above(The variable ...... parameter) Why does java not allow multiple variable length

I have a method public boolean findANDsetText (String Description, String ... extra ) { inside I want to call another method and pass it extras but I want to add new element (Description) to extras. object_for_text = getObject(find_arguments,extra); How can I do that in java? What would the code look like? I tired to accommodate code from this question but couldn't make it work. extra is just a String array. As such: List<String> extrasList = Arrays.asList(extra); extrasList.add(description); getObject(find_arguments, extrasList.toArray()); You may need to mess with the generic type of

I have declared the following method: private void mockInvokeDBHandler(Map<String, Object>... rows) { List<Map<String, Object>> allRows = Arrays.asList(rows)); // rest of method omitted } It is invoked by clients using something like Map<String, Object> row1 = new HashMap<String, Object>(); Map<String, Object> row2 = new HashMap<String, Object>(); mockInvokeDBHandler(row1, row2); However, the last line shown above generates a warning Type safety : A generic array of Map is created for a varargs parameter I don't fully understand this, but I guess it's because varargs params are converted to

According to this source code for the Arrays class, the method asList passes an array to the constructor of new ArrayList . But there is no such constructor. Doesn't varargs generate an array, so how is this possible? Here is the asList source: public static <T> List<T> asList(T... a) { return new ArrayList<T>(a); } java.util.Arrays.ArrayList is a different class than java.util.ArrayList . 来源： https://stackoverflow.com/questions/12015980/arrays-aslist-confusing-source-code

I'm using gcc 4.6. Assume that there is a vector v of parameters I have to pass to a variadic function f(const char* format, ...). One approach of doing this is: void VectorToVarArgs(vector<int> &v) { switch(v.size()) { case 1: f("%i", v[0]); case 2: f("%i %i", v[0], v[1]); case 3: f("%i %i %i", v[0], v[1], v[2]); case 4: f("%i %i %i %i", v[0], v[1], v[2], v[3]); // etc... default: break; } } // where function f is void f(const char* format, ...) { va_list args; va_start (args, format); vprintf (format, args); va_end (args); } The problem is of course that it does not support an arbitrary

I have some varargs system function, where T is some actual type, like String : sys(T... args) I want to create own function, which delegates to the system function. My function is also a varargs function. I want to pass through all the arguments for my function through to the system function, plus an additional trailing argument. Something like this: myfunc(T... args) { T myobj = new T(); sys(args, myobj); // <- of course, here error. } How do I need to change the line with the error? Now I see only one way: create array with dimension [args] + 1 and copy all items to the new array. But maybe

While playing about with optimisation settings, I noticed an interesting phenomenon: functions taking a variable number of arguments ( ... ) never seemed to get inlined. (Obviously this behavior is compiler-specific, but I've tested on a couple of different systems.) For example, compiling the following small programm: #include <stdarg.h> #include <stdio.h> static inline void test(const char *format, ...) { va_list ap; va_start(ap, format); vprintf(format, ap); va_end(ap); } int main() { test("Hello %s\n", "world"); return 0; } will seemingly always result in a (possibly mangled) test symbol