怎么在类中定义string类型的常量?

如何在类中定义string类型的常量??
java中这样写
public   final   static   String   BACKGROUND   = "/img/background.png ";
在c++中该怎样写呢?  
谢谢各位了.

[解决办法]
class A
{
public:
A():str( "abc "){}
const string str;
};

int main()
{
A a1, a2, a3;
cout < < a1.str < < endl;
cout < < a2.str < < endl;
cout < < a3.str < < endl;

return 0;
}