我们如何在 Java 中编写浮点数的二进制、八进制和十六进制文字？

Question

How we can write binary, octal and hexadecimal literals of floating point numbers in Java? Either in scientific or in normal representation.

class First
{
        public static void main(String[] args)
        {
                double b = 0x12p3;
                System.out.println(b);
        }
}

The above program results 144.0

class First
{
        public static void main(String[] args)
        {
                double b = 0x12e3;
                System.out.println(b);
        }
}

The above program results 4835.0

class First
{
            public static void main(String[] args)
            {
                    double b = 0x12e3;
                    System.out.println(b);
            }
}

The above program results 4835.0

class First
{
            public static void main(String[] args)
            {
                    double b = 012e3;
                    System.out.println(b);
            }
}

The above program results 12000

Please explain above outputs.

Answer 1

The first example is a HexadecimalFloatingPointLiteral, (16+2)*8 = 144.

The second and third example is actually a HexIntegerLiteral assigned to a double variable, 1*16*16*16 + 2*16*16 + 14*16 + 3 = 4835. Note that the 'e' is just the hex digit for 14.

The last example is a DecimalFloatingPointLiteral, 12 * 1000.

Java does not support an octal floating point literals.

For all the details see the JLS: https://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#jls-3.10.2