Doubt with constructor overloading

[Gitesh Ramchandani]

source http://www.valoxo.ch/jr/mocks/mock01a.html Q42

What is the output of the following code when compiled and run? Select one correct answer.
public class Question42{
Question42(byte b){System.out.println("in byte");}
Question42(short s){System.out.println("in short");}
Question42(char c){System.out.println("in char");}
Question42(int i){System.out.println("in int");}
public static void main(String[] args){
Question42 q42 = new Question42(2);
}
}

A. Prints: in int

B. Prints: in char

C. Prints: in byte

D. Prints: in short

E. Compilation error because of ambiguous constructor invocation.

Ans: A
Doubt: why not C as it is the best match?


pls help,
Gitesh
[ September 06, 2007: Message edited by: Gitesh Ramchandani ]

[paddy Mahadeva Iyer]

The value 2 could be set into byte int and short also if am not wrong. There is no way to identify who should be given preference. I think thats the reason for compilation to fail.

[greg buela]

A number literal that is less than long, is taken as int, even if it fits a smaller type.
By the way, this is not constructor overriding, but overloading.

[Gitesh Ramchandani]

If I modify the question as follows:

public class tt{
tt(float b){System.out.println("in float");}
 
tt(double i){System.out.println("in double");}
public static void main(String[] args){
tt q42 = new tt(2);
}
}

I get answer:

in float

In the above case whats happening as compared to my doubt in 1st post?

Please help,
Gitesh

[Burkhard Hassel]

Howdy, cowboys!

You cannot override constructors, because they are not inherited.
You are talking about overloading - and be prepared for text-only questions that will test your knowledge about nomenclature as well.
You should not mix the technical terms, not even in talking to your co-ranchers.

The question does not necessarily has anything to do with constructors at all, the same would work with methods:

class Main {
public static void main(String[] args) {
foo(2);
bar(2);
}
static void foo(byte b) {
System.out.println("byte");
}
static void foo(int i) {
System.out.println("int");
}
static void bar(float f) {
System.out.println("float");
}
static void bar(double d) {
System.out.println("double");
}
}
 

prints:
int
float



In the first part, no type conversion is needed, so foo just takes an int as the int number.
In the second part, there is no bar method for an int parameter, so in this case the compiler takes the "slowest" higher method possible.


Quizzzzz:
What constructor will be chosen here?

class Main2 {
public static void main(String[] args) {
new Main2 (2);
}
 
Main2(byte b) {
System.out.println("byte");
}
 
Main2(short s) {
System.out.println("short");
}
 
}

;)

Yours,
Bu

[Gitesh Ramchandani]

Bu thanks..

well i compiled the quiz, it is looking for an int constructor.

I got my answer thanks.