var-args and overloading

[Amitav Chowdhury]

Can some one tell me why the following code does not compile ?

public class Overloading {

	static void overload(int... d){
		System.out.println("Integer");
	}
	
	static void overload(double... d){
		System.out.println("Double");
	}
	
	public static void main(String args[]) {
		int i=1;
		overload(i);
	}
}

[Harpreet Singh janda]

Because int is applicable for both - int and double.

If you try by passing a double value, it will work fine

[Rajeev Rnair]

Because int can be widened to a double, so it gives ambigous method.
If you change the double to a short, it will compile
Or else instead of passing int you can pass a float or double.

public class Overloading { 

	static void overload(int... d){ 
		System.out.println("Integer"); 
	} 

//	static void overload(double... d){ 
//		System.out.println("Double"); 
//	} 
	
	static void overload(short... d){ 
		System.out.println("Short"); 
	} 
	
	public static void main(String args[]) { 
		int i=1; 
		overload(i); 
	} 
} 

[Amitav Chowdhury]

Following the same logic below code should not compile:

public class Overloading {

	static void overload(Integer x){
		System.out.println("Integer");
	}
	
	static void overload(Double d){
		System.out.println("Double");
	}
	
	public static void main(String args[]) {
		int i=1;
		overload(1);
	}
}

But it compiles fine giving the ouput "Integer". Any idea why the behaviors are different for var-args and auto boxing?

[W. Joe Smith]

Amitav Chowdhury wrote:Following the same logic below code should not compile:

public class Overloading {

static void overload(Integer x){
System.out.println("Integer");
}

static void overload(Double d){
System.out.println("Double");
}

public static void main(String args[]) {
int i=1;
overload(1);
}
}

But it compiles fine giving the ouput "Integer". Any idea why the behaviors are different for var-args and auto boxing?

I suggest looking at this link here. It explains some basic rules of widening, boxing and var-args.

[rushikesh sawant]

Wrappers are peers to each other. They cannot be converted from one type to other.

[Rajeev Rnair]

rushikesh sawant wrote:Wrappers are peers to each other. They cannot be converted from one type to other.

very correct!
All wrapper classes inherit from abstract class "Number" except for Boolean and Character.
A Double is a Number
An Integer is a Number
But Double is NOT an Integer


hope this helps!