casting

问题 I'm creating a Canvas object ( lines, vertices, triangle, ...) and I would like to apply to them a rotation around a point. I can't use the rotate() method of Canvas because points are attached to GeoPoint on a Map, so if I use the rotate() method the all map is rotating ... The problem is that Canvas needs Point(int,int) and applying a rotation creates double because of cos and sin functions. So when I apply the rotation to the all points, because of casting double to int, I have some

问题 Is it possible to cast from an InputStream to an AudioInputStream? I want to play little sound files at certain events, so I made following SoundThread import java.io.*; import javax.sound.sampled.*; public class SoundThread implements Runnable{ private String filename; SoundThread(String filename) { this.filename = filename; } public void run() { try { InputStream in = ClassLoader.getSystemResourceAsStream("sounds/"+filename+".wav"); Clip clip = AudioSystem.getClip(); clip.open(

问题 CODE struct A { }; // virtual details there, but left out struct B { }; // virtual details there, but left out struct C : A, B { }; // virtual details there, but left out C c; B& b = c; A& a = dynamic_cast<A&>( b ); // will this cast succeed at run-time? Note that I have left out the virtual details to keep the code simple. If dynamic_cast<> is limited to direct casts along the inheritance hierarchy, then I expect the code above to fail at run-time (because B& is unrelated to A&). However, if

问题 I'm implementing List interface to a class which stores data in a <T> type array. This raises problems with methods that take Collection as parameters, since collection stores it's objects as Object . How can I transform Object to T ? Simple casting doesn't work. class MyCollection<T> implements List<T>{ T[] tab; MyCollection() { this.tab = (T[])new Object[10]; } public boolean addAll(Collection c){ for(Object o : c){ o = (T)o; for(int i = 0; i < tab.length; i++){ tab[i] = o; } } } } I'm

问题 I'm implementing List interface to a class which stores data in a <T> type array. This raises problems with methods that take Collection as parameters, since collection stores it's objects as Object . How can I transform Object to T ? Simple casting doesn't work. class MyCollection<T> implements List<T>{ T[] tab; MyCollection() { this.tab = (T[])new Object[10]; } public boolean addAll(Collection c){ for(Object o : c){ o = (T)o; for(int i = 0; i < tab.length; i++){ tab[i] = o; } } } } I'm

问题 I need to cast a return value to a specific type that I need to keep dynamic, like let cellType = "CellTypeToBeResolved" cell = (tableView.dequeueReusableCellWithIdentifier("myID") as? CellTypeToBeResolved)! How is this possible in Swift 2.0? Thnx! 回答1: You can't do it, because Swift is (deliberately) missing not one but two pieces of the puzzle: You can't turn a string into a class. More important, you can't cast down to a class expressed as a variable. The class to cast down to must be a

问题 As far as I understand, Java Generics erases all the information concerning the parameter type T in the generic method (or in the generic class). That's why we can't use new expression, such as new T() instanceof expression, such as if(obj instanceof T) inside a generic method. My question is how the parameter type T works inside a generic method when it comes to casting. For example, I have 3 simple classes here: public class People { String name; public String getName() { return name; }

问题 What's the best/most cannonical way of passing in a constant integer value to a function that expects a pointer? For example, the write function write (int filedes, const void *buffer, size_t size); Let's say I just want to write a single byte (a 1), I would think this: write (fd, 1, 1); but I obviously get the warning warning: passing argument 2 of 'write' makes pointer from integer without a cast I know I can do int i = 1; write (fd, &i, 1); but is that necessary? What's the most correct

问题 Is there any difference between the following three casts for extracting raw byte pointers for use in pointer arithmetic? (assume a platform where char is 1 byte.) static_cast<char*>((void*)ptr)) reinterpret_cast<char*>(ptr) (updated) or: static_cast<char*>(static_cast<void*>(ptr)) Which should I prefer? In more detail... Given pointers to two member objects in a class, I would like to compute an offset from one to the other, so that I can reconstruct the address of one member given an offset

问题 Is there any difference between the following three casts for extracting raw byte pointers for use in pointer arithmetic? (assume a platform where char is 1 byte.) static_cast<char*>((void*)ptr)) reinterpret_cast<char*>(ptr) (updated) or: static_cast<char*>(static_cast<void*>(ptr)) Which should I prefer? In more detail... Given pointers to two member objects in a class, I would like to compute an offset from one to the other, so that I can reconstruct the address of one member given an offset