单例模式---饿汉式

Java代码： 

class Sign{
	//类加载时初始化，不延迟加载,类加载时是线程安全的   效率低
	private static Sign s = new Sign(); 
	
	//私有化构造器
	private Sign(){}
	
	//线程安全 ，效率高
	public static Sign getInstance(){
		return s; 
	}
}

public class Test{
	public static void main(String[] args) {
		Sign s1 = Sign.getInstance();
		System.out.println(s1);
		Sign s2 = Sign.getInstance();
		System.out.println(s2);
	}
}

 

运行结果：

javaTestpack.Fil@139a55
javaTestpack.Fil@139a55

C++代码:

#include <stdlib.h>
#include <stdio.h>

class Singlton {
private:
	Singlton(){}

public:
	static Singlton* GetInstance() {
		return sln;
	}


private:
	static Singlton* sln;
};

// 饿汉式
Singlton* Singlton::sln = new Singlton();

int main(){
	Singlton* pSln = Singlton::GetInstance();
	Singlton* pSln2 = Singlton::GetInstance();

	if (pSln2 == pSln){
		printf("pSln2 == pSln \n");
	}
	else {
		printf("pSln2 != pSln \n");
	}

	system("pause");
	return 0;  
}

 

 

总结：

1.构造器私有化

2.(Java)类加载时初始化类对象，线程安全的  (C++)sln属于全局变量区

3.函数直接调用线程安全