类包含一个类他的构造函数怎么写

Question

class   B 
        { 
                private   int   b; 
                private   A   ba=new A(b); 
                      
        }

Answer 1

class   B 
        { 
                private   int   b; 
                private   A   ba; 
                public B()
                {
                        ba = new A();
                }
                      
        }