singleton

作用：

1 保证类只实例化一次

2 提供全局访问接口

java实现

/**
 * 单例模式
 */
public class Singleton {
	
	private static Singleton singleton = null;//
	
	private Singleton()
	{
		
	}
	
	public static Singleton getInstance()
	{
		if(singleton==null)singleton = new Singleton();
		
		return singleton;
	}
	
	public static void main(String[] args) {
		Singleton s = Singleton.getInstance();
	}

}

c++实现

Singleton.h

#pragma once
class Singleton
{
private:
	static Singleton* singleton;

private:
	Singleton(void);

public:
	static Singleton* getInstance();

};

Singleton.cpp

#include "StdAfx.h"
#include "Singleton.h"

Singleton* Singleton:: singleton=0;

Singleton::Singleton(void)
{
}

Singleton* Singleton::getInstance()
{
	if(singleton==0) singleton = new Singleton();

	return singleton;
}

更多复杂用法，涉及并发访问及同步效率问题

http://www.iteye.com/topic/575052

单例模式的7种写法（基本都与线程安全相关）

http://cantellow.iteye.com/blog/838473

c++单例的几种写法，涉及自动析构和线程安全

http://blog.csdn.net/boyxiaolong/article/details/6645681