IS-A relationship

[Saibabaa Pragada]

Hi, This is part from K&B mock exam question.

In some cases, is-a relationships are used in the process of autoboxing.: TRUE..How ?? Please provide an example.
Given Explanation : For instance, you can autobox an int to a Number (via an Integer).

[Henry Wong]

Saibabaa Pragada wrote:
Given Explanation : For instance, you can autobox an int to a Number (via an Integer).

Like this?....

Number n = 24;

[Saibabaa Pragada]

I tried this using IS-A relation but I am getting compile error. Don't know where I am going wrong

class AAA {
    int aaa() {
	return 0;
    }

    Integer bbb() {
	return 0;
    }
}

public class Question52_Overrding_Asked extends AAA {
    Integer aaa() {//The return type is incompatible with AAA.aaa()
	return 0;
    }

    int bbb() {//The return type is incompatible with AAA.bbb()
	return 0;
    }
}

Henry Wong wrote:

Saibabaa Pragada wrote:
Given Explanation : For instance, you can autobox an int to a Number (via an Integer).

Like this?....

Number n = 24;

[Prasad Kharkar]

actually this is related to overriding
in the subclass
you are writing the method which override the superclass methods
and overriding method rules say that

the return type should be same or the subclass of the return type
This is not about boxing and unboxing

[Saibabaa Pragada]

Hi Prasad, I think you are referring about covariant return types. I am looking for this "In some cases, is-a relationships are used in the process of autoboxing.: TRUE..How ?? Please provide an example, that would be really helpful. "

[Prasad Kharkar]

Then your query is simple
this is a sample program that can make you understand the concept
here we are returning an int value that is getting autoboxed into Integer
and Integer IS-A Number
so return type Number is also valid

this is called as Boxing and then Widening

class ABC {
	
	public Number go(){
		int s = 10;
		return s;
	}

	public static void main(String[] args) {
		System.out.println(new ABC().go());
	}
}

hope this helps now

[Saibabaa Pragada]

Great..Thanks Prasad !!