Assignment doubt

[Edisandro Bessa]

Hi guys,

Can you please explain why the code in bold are illegal ?

I'm a little bit confused.

class Test{
    public static void main(String ... args){
        final int i = 100;
        final long l = 10;
        byte b1 = i;
 
        // byte b2 = l; [B]Illegal[/B]
        
        [B]// final variable can be assigned to byte but cannot be passed
        // as argument ?[/B]
        // doSomething(i); 
 
        doSomething(b1);
    }
    
    public static void doSomething(byte b){
        System.out.println("Doing something");
    }
}

[Keith Lynn]

This is from the Java Language Specification.

In addition, a narrowing primitive conversion may be used if all of the following conditions are satisfied:

* The expression is a constant expression of type byte, short, char or int.
* The type of the variable is byte, short, or char.
* The value of the expression (which is known at compile time, because it is a constant expression) is representable in the type of the variable.

If the type of the expression cannot be converted to the type of the variable by a conversion permitted in an assignment context, then a compile-time error occurs.

[Edisandro Bessa]

Thanks Keith. Now I see the problem with the assignment byte b2 = l

But what about the method call ?
Such method expects a byte but I'm passing an int constant. I don't think the rules applied here are the same for variables. Could you please explain.
[ April 11, 2006: Message edited by: Edisandro Bessa ]

[Keith Lynn]

On the method call, you are sending a byte as parameter.

[Edisandro Bessa]

Keith,

The commented call // doSomething(i); doesn't compile. I'm trying to send a final int to a method which expects a byte.

Could you please explain why it's not allowed once it's allowed to assign a final int to a byte ?

Are method arguments assignment rules different from variable assignment rules ?
[ April 11, 2006: Message edited by: Edisandro Bessa ]

[Keith Lynn]

I think the context of what I showed from the Java Language Specification was specifically for assignments of variables. I don't think it applies to method calls.

[marc weber]

See JLS, 5.3 Method Invocation Conversion.