I have a problem with the below
byte b = 10; byte r = (byte) (b * b);// giving correct result byte r = (byte) b * b;// giving error " POSSIBLE LOSS OF PRECISION"
Why is it mandatory to give parentheses to
b * b?
(byte) b * b casts the value of the first
byte (which is redundant since it was already
byte), and multiples it by the value of the second
b. Multiplying two
bytes promotes them to
int first, since there is no
* operator for
bytes. Therefore the result is
int, and cannot be assigned to a
On the other hand,
(byte)(b * b) casts the
int multiplication result to
byte, which can be assigned to a
This is covered in the JLS in 5.6.2. Binary Numeric Promotion:
When an operator applies binary numeric promotion to a pair of operands, each of which must denote a value that is convertible to a numeric type, the following rules apply, in order:
If any operand is of a reference type, it is subjected to unboxing conversion (§5.1.8).
Widening primitive conversion (§5.1.2) is applied to convert either or both operands as specified by the following rules:
If either operand is of type double, the other is converted to double.
Otherwise, if either operand is of type float, the other is converted to float.
Otherwise, if either operand is of type long, the other is converted to long.
Otherwise, both operands are converted to type int.