Singleton 模式 Java,c++实现

 对于某些类，我们需要保证系统中只能有一个实例，这种类的设计用到singleton模式模式。

单线程的singleton模式是 straightforward的，下面给出Java和C++11的线程安全singleton实现

Java：

public class Singleton {
	private static Singleton instance = null;
	private static Object mutex = new Object();
	
	private Singleton() { }
	
	public static Singleton getInstance() {
		if(instance == null) {
			synchronized(mutex) {
				if(instance == null)
					instance = new Singleton();
			}
		}
		return instance;
	}
}

　　

C++:

static Singleton& get(){
  static Singleton instance;
  return instance;
}

C++11 remove the need for manual locking. Concurrent execution shall wait if a static local variable is already being initialized.