增加单例的饿汉模式支持，饿汉单例模式本身是多线程安全的

06.Singleton/2.Code/Singleton/Singleton.h

@@ -6,28 +6,45 @@
 #include <mutex>
 using namespace std;
 
-class Singleton
+class Singleton_Lazy
 {
 public:
-	static Singleton* getInstance(){
+	static Singleton_Lazy* getInstance(){
+		printf("This is Singleton Lazy mode...\n");
 		if (instance == NULL){
 			m_mutex.lock();
 			if (instance == NULL){
 				printf("创建新的实例\n");
-				instance = new Singleton();
+				instance = new Singleton_Lazy();
 			}
 			m_mutex.unlock();
 		}
 		return instance;
 	}
 private:
-	Singleton(){}
+	Singleton_Lazy(){}
 
-	static Singleton* instance;
+	static Singleton_Lazy* instance;
 	static std::mutex m_mutex;
 };
 
-Singleton* Singleton::instance = NULL;
+Singleton_Lazy* Singleton_Lazy::instance = NULL;
-std::mutex Singleton::m_mutex;
+std::mutex Singleton_Lazy::m_mutex;
+
+
+class Singleton_Hungry
+{
+public:
+	static Singleton_Hungry* getInstance() 
+	{
+		printf("This Singleton Hungry mode...\n");
+		return instance;
+	}
+private:
+	Singleton_Hungry() {}
+	static Singleton_Hungry* instance;
+};
+
+Singleton_Hungry* Singleton_Hungry::instance = new Singleton_Hungry;
 
 #endif //__SINGLETON_H__

06.Singleton/2.Code/Singleton/main.cpp

@@ -53,9 +53,18 @@ int main()
 #else
 #define THREAD_NUM 5
 #include<pthread.h>
-void* callSingleton(void *pPM)
+void* callSingleton_Lazy(void *pPM)
 {
-	Singleton *s = Singleton::getInstance();
+	Singleton_Lazy *s = Singleton_Lazy::getInstance();
+	pthread_t nThreadNum = pthread_self();
+	// sleep(50);
+	printf("线程编号为%ld\n", nThreadNum);
+	return 0;
+}
+
+void* callSingleton_Hungry(void *pPM)
+{
+	Singleton_Hungry *s = Singleton_Hungry::getInstance();
 	pthread_t nThreadNum = pthread_self();
 	// sleep(50);
 	printf("线程编号为%ld\n", nThreadNum);
@@ -66,11 +75,20 @@ int main()
 {
 	pthread_t threads_pool[THREAD_NUM];
 	int tids[THREAD_NUM];
+	printf("Singleton Lazy mode:\n");
 	for(int i = 0; i < THREAD_NUM; i++) 
 	{
-		tids[i] = pthread_create(&threads_pool[i], NULL, callSingleton, NULL);
+		tids[i] = pthread_create(&threads_pool[i], NULL, callSingleton_Lazy, NULL);
 		pthread_join(threads_pool[i], (void**)&tids[i]);
 	}
+
+	printf("Singleton Hungry mode:\n");
+	for(int i = 0; i < THREAD_NUM; i++) 
+	{
+		tids[i] = pthread_create(&threads_pool[i], NULL, callSingleton_Hungry, NULL);
+		pthread_join(threads_pool[i], (void**)&tids[i]);
+	}
+
 	return 0;
 }