从另一个调用构造函数 - this 关键字的用法

Question

Q. Identify the valid option which is used to invoke the no argument constructor, Product(), at Line 1.

class Product{
   int productId;
   String productName;

   Product( )   {
         productId=0; productName="";
  } 

   Product(int id, String name)   {
        //access Product() ---- Line 1
        productId=id;
        productName=name;
   } 
}

A. this();

Can you help me understand how 'this' reference variable can be used here?

Answer 1

Can you help me understand how 'this' reference variable can be used here?

this() isn't using a variable.

It's a special syntactic construct which says "invoke another constructor in the same class". It's called an "explicit constructor invocation" (or, more specifically, an " alternate constructor invocation "), and can only appear as the first statement in the constructor (see language spec ).

However, you can use this as a "variable" later in the constructor, in order to access member variables or instance methods on the instance which is currently being constructed, for instance:

this.productId = id;