Hello Experts, is final Map<Integer,Map<String,Integer>> status = new ConcurrentHashMap<Integer, Map<String,Integer>>(); Map<Integer,Map<String,Integer>> statusInner = new ConcurrentHashMap<Integer, Map<String,Integer>>(); status.put(key,statusInner); the same as volatile Map<Integer,Map<String,Integer>> status = new ConcurrentHash...
Say I have two threads and an object. One thread assigns the object: public void assign(MyObject o) { myObject = o; } Another thread uses the object: public void use() { myObject.use(); } Does the variable myObject have to be declared as volatile? I am trying to understand when to use volatile and when not, and this is puzz...
I think i have a pretty good idea about the volatile keyword in java, but i'm thinking about re-factoring some code and i thought it would be a good idea to use it. i have a class that is basically working as a DB Cache. it holds a bunch of objects that it has read from a database, serves requests for those objects, and then occasional...
I saw it was possible to do it but I do not understand the interest. ...
I occasionally use a volatile instance variable in cases where I have two threads reading from / writing to it and don't want the overhead (or potential deadlock risk) of taking out a lock; for example a timer thread periodically updating an int ID that is exposed as a getter on some class: public class MyClass { private volatile int ...
Can the volatile be used for class objects? Like: volatile Myclass className; The problem is that it doesn't compile, everywhere when some method is invoked, the error says: error C2662: 'function' : cannot convert 'this' pointer from 'volatile MyClass' to 'MyCLass &' What is the problem here and how to solve it? EDIT: class Queue ...
In a nice article with some concurrency tips, an example was optimized to the following lines: double getBalance() { Account acct = verify(name, password); synchronized(acct) { return acct.balance; } } If I understand that correctly, the point of the synchronization is to ensure that the value of acct.balance that are read by ...
[edit] For background reading, and to be clear, this is what I am talking about: Introduction to the volatile keyword When reviewing embedded systems code, one of the most common errors I see is the omission of volatile for thread/interrupt shared data. However my question is whether it is 'safe' not to use volatile when a variable is ...
Mmap returns a void*, but not a volatile void*. If I'm using mmap to map shared memory, then another process could be writing to that memory, which means two subsequent reads from the same memory location can yield different values -- the exact situation volatile is meant for. So why doesn't it return a volatile void*? My best guess is ...
Having this code: typedef volatile int COUNT; COUNT functionOne( COUNT *number ); int functionTwo( int *number ); I can't get rid of some warnings.. I get this warning 1 at functionOne prototype [Warning] type qualifiers ignored on function return type and I get this warning 2, wherever I call functionTwo with a COU...
More specifically, I have (simplified) the following: union foo { volatile int bits; char data[sizeof(int)*CHAR_BIT]; } If I never access the first sizeof(int) items of data, can i rely on bits working as expected? ...
I have a class that has a few arraylists in it. My main class creates a new instance of this class. My main class has at least 2 threads adding and removing from my class with the arraylists in it. At the moment everything is running fine but I was just wondering if it would be safer to declare my class with the arraylists in it as vol...
Let's assume I'm implementing a Winforms UI where all commands adhere to the following pattern: interface ICommand { bool CanExecute { get; } void Execute(); } Buttons or menu items that trigger such a command should have the following set-up: property Enabled is bound to the command's CanExecute event Click is linked to the...
Hello guys, In C++, volatile is treated the same way const is: passing a pointer to volatile data to a function that doesn't want the volatile modifier triggers a compile error. int foo(int* bar) { /* snip */ } int main() { volatile int* baz; foo(baz); // error: invalid conversion from ‘volatile int*’ to ‘int*’ } Why is it d...
I have a function whose prototype is as follows: void foo(const char * data); Elsewhere in my code, I have a global variable declared as follows volatile char var[100]; Whenever I try to do this: foo(var); The compiler throws up the following error message: Argument of type "volatile char *" is incompatible with parameter of ty...
Hi! I am wondering at the difference between declaring a variable as volatile and always accessing the variable in a synchronized(this) block in JAVA (particularly J2ME)? According to this article http://www.javamex.com/tutorials/synchronization_volatile.shtml there is a lot to be said and there are many differences but also some simila...
Ok so I just read this question http://stackoverflow.com/questions/106591/do-you-ever-use-the-volatile-keyword-in-java, and I get using a volatile variable in order to stop a loop. Also I've seen this reference, http://www.javamex.com/tutorials/synchronization_volatile.shtml. Now the article says that volatile variables are non-blocking....
I find myself wanting to write a routine that will operate on both volatile and non-volatile memory blocks. Something along the lines of: void byte_swap (unsigned * block_start, size_t amount) { for (unsigned * lp = block_start; lp < block_start + amount; lp++) { *lp = htonl(*lp); } memcpy (block_start, some_other_ad...
As I read deeper and deeper into the meaning of the volatile keyword, I keep saying to myself "this is way into implementation, this should not be a part of a high level programming language". I mean, the fact that CPUs cache the data should be interesting for the JIT compiler, not to the C# programmer. A considerable alternative might ...
I have a data class with lots of data in it (TV schedule data). The data is queried from one side and periodically updated from the other side. There are two threads: the first thread queries the data on request and the second thread updates the data on regular intervals. To prevent locking, I use two instances (copies) of the data class...