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Constructors of non static member classes take an extra hidden parameter which is a reference to an instance of the immediately enclosing class. There is also a syntactic extension of 'new'.

In the below code,

class K{ static class Ka{ static class Kb{ class Kc{ class Kd{ } } } } } class Test{ K.Ka.Kb.Kc.Kd k = new K.Ka.Kb().new Kc().new Kd(); }

Can you please help me understand the meaning of Kb() in K.Ka.Kb().new Kc().new Kd()? I understand that new Kc() is required as told in first paragraph.

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    only if you bothered reading this Commented Sep 8, 2015 at 14:52

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7

The parentheses you point out actually do not apply to Kb but K.Ka.Kb.

new K.Ka.Kb()

is creating a new instance of the K.Ka.Kb nested class.

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3 Comments

Oh you mean (new K.Ka.Kb()).new Kc().new Kd();?
@SotiriosDelimanolis kc and kd are inner class. But the idiom of saying non static member class as inner class, is it a standard jargon?
Yes
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It's calling the constructor of Kb. It's easier to show this in three statements:

K.Ka.Kb x1 = new K.Ka.Kb(); K.Ka.Kb.Kc x2 = x1.new Kc(); // Pass x1 as the hidden constructor arg K.Ka.Kb.Kd.Kd k = x2.new Kd(); // Pass x2 as the hidden constructor arg
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1

Kb() is the default constructor for class Kb. It is what relates to the first new of the line:

  1. you are creating a new instance of Kb (class K.Ka.Kb actually ; depending on the context you may omit K.Ka.)
  2. on which you are calling new Kc() for creating a new instance of Kc
  3. on which you are calling new Kd() for creating a new instance of Kd
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