what is correspoding feature for synchronized in java?
Use the following in C++:
#include <mutex>
std::mutex _mutex;
void f()
{
std::unique_lock<std::mutex> lock(_mutex);
// access your resource here.
}
Despite this question has been already answered, by the idea of this article I made my version of synchronized
keyword using just standard library (C++11) objects:
#include <mutex>
#define synchronized(m) \
for(std::unique_lock<std::recursive_mutex> lk(m); lk; lk.unlock())
You can test it like:
#include <iostream>
#include <iomanip>
#include <mutex>
#include <thread>
#include <vector>
#define synchronized(m) \
for(std::unique_lock<std::recursive_mutex> lk(m); lk; lk.unlock())
class Test {
std::recursive_mutex m_mutex;
public:
void sayHello(int n) {
synchronized(m_mutex) {
std::cout << "Hello! My number is: ";
std::cout << std::setw(2) << n << std::endl;
}
}
};
int main() {
Test test;
std::vector<std::thread> threads;
std::cout << "Test started..." << std::endl;
for(int i = 0; i < 10; ++i)
threads.push_back(std::thread([i, &test]() {
for(int j = 0; j < 10; ++j) {
test.sayHello((i * 10) + j);
std::this_thread::sleep_for(std::chrono::milliseconds(100));
}
}));
for(auto& t : threads) t.join();
std::cout << "Test finished!" << std::endl;
return 0;
}
This is just an approximation of synchonized
keyword of Java but it works. Without it the sayHello
method of the previous example can be implemented as the accepted answer says:
void sayHello(unsigned int n) {
std::unique_lock<std::recursive_mutex> lk(m_mutex);
std::cout << "Hello! My number is: ";
std::cout << std::setw(2) << n << std::endl;
}
There is no keyword in C++03 equivalent to synchronized
in Java . But you can use Mutex to guarantee safety of thread.