实例构造与结构构造(Java/C#)

所谓实例构造就是指通常的构造函数带参数的和不带参数的，其中不带参数的构造函数又叫做默认构造函数。而类型构造函数又可称为静态构造函数。例如：

publicclassCustomer...{
publicCustomer()...{...}//instanceconstructor,default
publicCustomer(Typetype)...{...}//instanceconstructorwithargument
staticCustomer()...{...}//typeconstructor
}

其中public Customer(),public Customer(Type type),为实例构造函数，static Customer为类型构造函数，当实例化一个这样的类的时候如：Customer customer = new Customer([Type type])时，CLR首先会调用类型构造函数，然后是实例构造函数。下面看个例子：

publicclassCustomer:Base...{
publicCustomer()...{
System.Console.WriteLine("Customerinstanceconstructorwasinvoked.");
}
staticCustomer()...{
System.Console.WriteLine("Customertypeconstructorwasinvoked.");
}
}
publicclassBase...{
publicBase()...{
System.Console.WriteLine("Baseinstanceconstructorwasinvoked.");
}
staticBase()...{
System.Conole.WriteLine("Basetypeconstructorwasinvoked.");
}
}

到创建Customer对象时候，customer = new Customer();时候有如下输出：

Customer type constructor was invoked.

Base type constructor was invoked.

Base instance was invoked.

Customer instance was invoked.

而在Java中却不一样，看下面的例子：

packagemf;
publicclassBase...{
publicBase()...{
System.out.println("Baseinstanceconstructorwasinvoked.");
}
static...{
System.out.println("Basetypeconstructorwasinvoked.");
}
}
publicclassCustomerextendsBase...{
publicCustomer()...{
System.out.println("Customerinstanceconstructorwasinvoked.");
}
static...{
System.out.println("Customertypeconstructorwasinvoked.");
}
}
publicclassTest...{
publicstaticvoidmain(String[]args)...{
Customercustomer=newCustomer();
}

}

其输出结果为：

Base type constructor was invoked.
Customer type constructor was invoked.
Base instance constructor was invoked.
Customer instance constructor was invoked.