Java Types Conversting & Casting .

Question

Hi All !
Really i do have two questions regarding Java Type Conversion and Casting
and hope i would find (good) answers :
[Q1:]
why it's legal to convert(implicitly) from ( long --> float ) and this is
said to be a widening conversion even if the size of long is longer than float
and hence there a possible loss of information ?
[Q2:]
why it's legal to cast(explicitly) from ( byte --> char ) and how compiler will deal
with byte as singed and char as unsigned during type casting (this is said to be
a narrowing converstion and it is really is ) ?
for [Q2:] i did the follwing code :
public class TestNarw
     public TestNarw()
          byte bBefore=-100; // change this value to whatever negative number that is to fit in a byte.
          char c=(char)bBefore;
          byte bAfter=(byte)c;
          System.out.println(bBefore);
          System.out.println(c);
          System.out.println(bAfter);
     public static void main(String args[])
          new TestNarw();
           the SURPRISE on the code above is that the output is :
-100
-100
and when i change the value of "bBefore" to any negative number that is to fit in a
byte it (e.g: -10) it gives the same value for the variable "c" (character)which is ASCII "63" ="?"
but when i test it with a suitable postive number , it works fine and the character (c) represents that number
so how it deals with converstion from negative byte to char ?
Thanks ...

Answer 1

Q1: you can always cast between primitive types (numbers, not boolean). The only problem is you lose precision in certain directions. A long to float isn't necessarily going to change the value, but it really depends on the long value. If it's out of range of float, it'll basically be wrapped around to the negative side. (at least that's what long to int would do, not sure if float or double behave different in that regard).
Q2: The value -100 converted to a char would probably be 65436, which prints as "?" because DOS can't print that character. Then when you cast back, 65436 is out of range for a byte, so it rolls back around to -100.
Try this:
byte b = 127;
System.out.println(b);
System.out.println((byte)b+1);
System.out.println((byte)0xFF); // 255 in hex
It'll print 127, then -128, then -1. When you go out of range, it just wraps around. For this reason, you often have to be carefull what size you store things as.