如何在java中实例化成员类的数组

Question

I have a class called MultiplePrintableInvoiceData, and this class has an inner class which is a member class called Product.

I can instantiate an instance of Product in another class with the following code:

MultiplePrintableInvoiceData pid = new MultiplePrintableInvoiceData();
MultiplePrintableInvoiceData.Product product = pid.new Product();

but when I try to instantiate an array of Product with the following code:

MultiplePrintableInvoiceData.Product[] product = pid.new Product[];

I get a compilation error: "(" expected - illegal start of expression. Please I need help.

Update I have modified the code to:

MultiplePrintableInvoiceData.Product[] product = pid.new Product[11];

But it is still giving me an error!

Answer 1

It's not possible to create an object of the inner class unless we already have an object of the outer class. This is because the object of the inner class is quietly connected to the object of the outer class that it was made from. However, if you make a nested class (a static inner class), then it doesn't need a reference to the outer-class object.

However, This is not the case while creating an array of inner class. We can't use Object of outer class for referencing to inner class while creating Array of inner class. because, we are not creating any inner objects. We are only creating an array, which is just a place to put inner objects. It does not need to belong to any outer objects.

  class Outer
  {
      class Inner
      {
        // field declaration and other code
      }
  }
  //...........
  Outer outerObj = new Outer();
  Outer.Inner innerObj = outerObj.new Inner(); // instance creation of inner class

  Outer.Inner[] innrArr = new Outer.Inner[5]; // array creation of inner class

For your context, You need to do:

MultiplePrintableInvoiceData.Product[] product = new MultiplePrintableInvoiceData.Product[10];