Doubt

[Raj Neets]

Hai
Iam reading mughal book for JCP, on pg 48 author say that u need explicit cast to assign character to short or byte.
but short s1 ='a';
byte b1='A';
the above piece of code compile and gives result.
can some explain it to me.
Thax
Raj

[Jessica Sant]

Now try this:

public class implicitTests
{
   public static void main( String[] args )
   {
      char c1 = 'a';  // works fine, as expected
      short s1 = 'a'; // works fine, the compiler KNOWS that 'a' can fit in a short
      byte b1 = 'a';  // works fine, the comiler KNOWS that 'a' can fit in a byte
      short s2 = (short) c1;  // ack! the compiler can't be sure what c1 is,
                              //doesn't know if it can fit in a short!
                              //requires explicit cast
      byte b2 = (byte) c1;    // ack! the compiler can't be sure what c1 is,
                              //doesn't know if it can fit in a byte!
                              //requires explicit cast
      
      final char c2 = 'f';
      byte b3 = c2;   // no problem c2, is final so the compiler can be sure 
                      //it will fit in byte.
      short s3 = c2;  // no problem c2, is final so the compiler can be sure
                      //it will fit in byte.
   }
}

does that help explain things?
[ February 06, 2003: Message edited by: Jessica Sant ]

[Rahul Gupta]

hi raj,
here is the complete picture
byte->short->int->long->float->double
                    ^
                    |
                    char
This means that while traversing in the direction of the arrow no explicit cast is required. But while traversing in the opposite direction explicit cast is required. Also explicit cast is required when there is any conversion between (byte or short) and the char VARIABLES (not literals).
Hope that helps
rahul

[ February 06, 2003: Message edited by: Rahul Gupta ]
[ February 06, 2003: Message edited by: Rahul Gupta ]
[ February 06, 2003: Message edited by: Rahul Gupta ]
[ February 06, 2003: Message edited by: Rahul Gupta ]

[Pallavi Chakraborty]

Hello Jessica,
I wanted to clarify something, from your answer.
When char c1 = 'a' is not declared as final, it means that the value of a may change into something which will not fit into a char or a byte and the compiler doesn't want to take chances.
With - final char c2 = f - the complier knows for sure.
Thank you
Pallavi

[Sarma Lolla]

I wanted to clarify something, from your answer.
When char c1 = 'a' is not declared as final, it means that the value of a may change into something which will not fit into a char or a byte and the compiler doesn't want to take chances.

In the chain of clarifications I want to correct Pallvi.
when char c1='a'; value of c1 can change to some thing else later but not 'a'. When c1 is assigned to a short without cast compiler generates error.

[Pallavi Chakraborty]

Hello Sarma,
Can you explain the last sentence of your answer in a little more detail?
I think I am missing something in my understanding.
Thank you very much
Pallavi

[Tom Adams]

I think the point here is what char values will or will not fit into a short. Since short is signed its high order bit is not avail for data.
short only has 15 bits avail for data where char has 16.
A = 0x0041 (fits fine)
32767 (0x7FFF) would be the largest char that would fit into a short.
Thus the compiler will only let the statement pass if he knows the data can fit into 15 bits. This can only be the case with literals or final variables.
At least that is my theory...
[ February 07, 2003: Message edited by: Tom Adams ]

[Sarma Lolla]

Iam reading mughal book for JCP, on pg 48 author say that u need explicit cast to assign character to short or byte.
but short s1 ='a';
byte b1='A';
the above piece of code compile and gives result.
can some explain it to me.

Pallvi,
This entire POST startwed with the question what can be assigned to a short and what not.
So my clarification is in accordance to what is asked above.
char c1='a';
short s1=c1; // error
final char c2='a';
short s2= c2; // OK
char c3='a';
short s3=(short)c3;

[Pallavi Chakraborty]

Hello Tom, Sarma
Thank you ..... Got it now.
Pallavi

[Pallavi Chakraborty]

Hello Tom, Sarma
Thank you ..... Got it now.
Pallavi

[Archana Annamaneni]

Thanks everybody ,It cleared my concepts about conversions
-Archana