Question on inner classes

[thejaka samarakoon]

public class Outer {
private int innerCounter;
class Inner {
Inner() {innerCounter++;}
public String toString() {
return String.valueOf(innerCounter);
}
}
private void multiply() {
Inner inner = new Inner();
this.new Inner();
System.out.print(inner);
inner = new Outer().new Inner();
System.out.println(inner);
}
public static void main(String[] args) {
new Outer().multiply();
}
}
    

In this example can anyone explain how we are getting 21 when runs?

[Abimaran Kugathasan]

There are two print statements. Have look on those? And, If I asked, how many outer objects are created and how many Inner objects?

[thejaka samarakoon]

1 outer object & 3 inner objects.Isn't it.

[Harpreet Singh janda]

2 outer and 3 inner objects.

  
class Outer {
	private int innerCounter;
	class Inner {
		Inner() {innerCounter++;}
		public String toString() {
			return String.valueOf(innerCounter);
		}
	}
	private void multiply() {
		Inner inner = new Inner();   -----------------------1.1 inner oject
		this.new Inner(); ------------------------------------1.2 innr object
		System.out.print(inner);
		inner = new Outer().new Inner();-------------------2 outer object and 2.1 inner object
		System.out.println(inner);
	}
	public static void main(String[] args) {
		new Outer().multiply();  ------------------------------1 outer object here
	}
}
  

Hope this helps.

[Abimaran Kugathasan]

I think, you got it. And If I further asked, what does the Inner object creation impact on the Outer object?

[thejaka samarakoon]

can you explain further how 21 comes as the out put

[Abimaran Kugathasan]

That isn't 21. 2 & 1. 2 from you 12th line and 1 from 14th line of your original program. Could you understand?

[thejaka samarakoon]

I got it.Thanks Abimaran Kugathasan & Harpreet Singh janda

[Abimaran Kugathasan]

Welcome!

[Shanky Sohar]

public class Outer {   
private int innerCounter;   
class Inner {   
Inner()----->this is a defaut constructor
 {innerCounter++;}   
public String toString() {   
return String.valueOf(innerCounter);   
}   
}   
private void multiply() {   
Inner inner = new Inner();--->this will invoke the default constructor whic is incrementing the value of innercounter to 1   
this.new Inner();         --->this will again invoke the default constructor whic is incrementing the value of innercounter to 2
System.out.print(inner);  --->this will print the value of innercounter which is written by toString() method  
inner = new Outer().new Inner();  ---this will again create a new object of inner which will invoke default construtor and value of innnercounter is incremented to 1 
System.out.println(inner);    -->it will print the value which is 1.
}   
public static void main(String[] args) {   
new Outer().multiply();-->it will call multiply()  method of class Outer  
}   
}  

Could you please QuoteYourSource next time you post the question