Conversion of long to float

[gayathri_jag]

Hi,
Is conversion of long to float possible automatically?
since float (32) precision and long is (64) precision.
in S& H book it says that it is possible.
confused?
gayathri

[Udayan Naik]

Yes Gayathri,the conversion from long to float is a conversion and not a cast.This is because the range of float is more than that of long.A variable of type long can represent only integral values while a float vraiable can represent integral as well as floating point values.

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[Sapna Mathur]

But isnt long to float a narrowing conversion?

[Oliver Grass]

Hi,
no, long to float isn't a narrowing conversion. It is a widening one.
On the first glance this seems strange cause float is 32-bit and long is 64-bit. BUT this has to do with the internal representation of integral and floating-point types. A long is represented as a 64-bit signed two's-complement integer. A float is represented using 32-bit IEEE 754 floating-numbers...
Sounds a little bit complex, but isn't. If you've never heard of these before, just ask, perhaps i or someone else can explain....
as always correct me if i'm wrong
Oliver

[SathishVJ]

Hi,
I don't know exactly why it works the way it does. Anyways, try out this piece of code. Apparently the JVM is approximating the the long to fit it into the float. The normal representation of floats and doubles being sign*mantissa*2^exponent, it allows the JVM to approximate (incorrectly) the long value into a certain number in the exponent.
So point is conversion is possible but is erroneous on large values.
public class test {
public static void main(String args[]){
long l = 123455432123456789l;
float f = 3.2f;
f = l;
System.out.println(f); //prints 1.23455433E17 or something similar
l = (long)f;
System.out.println(l); //prints 123455433309421568 or something similar
}
}
Hope I was able to help.
Regds
Sathish

[shailesh sonavadekar]

gayathri_jag & SathishVJ , as part of naming policy of the site user has to register with proper first name & last name. Gayatri & Satish , I request you to register yourself with proper last name & help javaranch to maintain decorum.