Casting hierarchy

[Willie Toma]

I'm not sure if my wording is exactly correct, so correct me if it's wrong....
It seems casting is necessary when initializing anything below a selected type on the list:
double
float
long
int
short/char
char/short
byte

Example:
double d = 9;
float f = (float)d; //Cast necessary
Question:
1) Example:

float f=8;
long l=(long)f;   //Cast necessary

Why is casting necessary between float and long even though float is 32 bits and long is 64 bits? Long is bigger, there should be plenty of room.
2)Example:

short s=1;
char c=(char)s;  //Cast necessary
char c2=2;
short s2=(short)c2;  //Cast necessary

I believe that short can hold an negative value, and char can't. So, a char can hold more than a short? and a cast is necessary. Why is a cast necessary both ways if one is bigger than the other?
3)Example:

char c3=3;
byte b=(byte)c3;  //Cast necessary
byte b2=4;
char c4=(char)b2;  //Cast necessary

Why is casting necessary both ways if char is 16 bits, and byte is 8 bits?
4)O'yea, by the way, thanks for you help!!!

[Jose Botella]

In JLS 5 all of this is explained.
Any assignment between char and short/byte is regarded as a narrowing conversion, and thus it needs a cast... Except the cases explained in JLS 5.2

[Willie Toma]

What is JLS? Java L... S...

[Patrick Hoey]

JLS,
Java Language Specification.
Get it here:
http://java.sun.com/docs/books/jls/index.html
You can download it in html, or pdf format (about 4.5 megs).