..생략..
final long Micro = 24 * 60 * 60 * 1000 * 1000;
final long Millis = 24 * 60 * 60 * 1000;
System.out.println(Micro/Millis);

<JLS 발췌>
5.1.2 Widening Primitive Conversion
The following 19 specific conversions on primitive types are called the widening
primitive conversions:
CONVERSIONS AND PROMOTIONS Widening Primitive Conversion 5.1.2

• byte to short, int, long, float, or double
• short to int, long, float, or double
• char to int, long, float, or double
• int to long, float, or double
• long to float or double
• float to double
Widening primitive conversions do not lose information about the overall
magnitude of a numeric value. Indeed, conversions widening from an integral type
to another integral type do not lose any information at all; the numeric value is
preserved exactly. Conversions widening from float to double in strictfp
expressions also preserve the numeric value exactly; however, such conversions
that are not strictfp may lose information about the overall magnitude of the
converted value.
Conversion of an int or a long value to float, or of a long value to double,
may result in loss of precision—that is, the result may lose some of the least significant
bits of the value. In this case, the resulting floating-point value will be a
correctly rounded version of the integer value, using IEEE 754 round-to-nearest
mode (§4.2.4).
A widening conversion of a signed integer value to an integral type T simply
sign-extends the two’s-complement representation of the integer value to fill the
wider format. A widening conversion of a char to an integral type T zero-extends
the representation of the char value to fill the wider format.
Despite the fact that loss of precision may occur, widening conversions
among primitive types never result in a run-time exception (§11).
Here is an example of a widening conversion that loses precision:
class Test {
public static void main(String[] args) {
int big = 1234567890;
float approx = big;
System.out.println(big - (int)approx);
}
}
which prints:
-46
thus indicating that information was lost during the conversion from type int to
type float because values of type float are not precise to nine significant digits.