Java 中 Long 到 Double 的转换

Question

Is there any way to convert a Long data type to Double or double ?

For example, I need to convert 15552451L to a double data type.

Answer 1

You could simply do :

double d = (double)15552451L;

Or you could get double from Long object as :

Long l = new Long(15552451L);
double d = l.doubleValue();

Answer 2

简单的铸造？

double d = (double)15552451L;

Answer 3

As already mentioned, you can simply cast long to double. But be careful with long to double conversion because long to double is a narrowing conversion in java.

Conversion from type double to type long requires a nontrivial translation from a 64-bit floating-point value to the 64-bit integer representation.Depending on the actual run-time value, information may be lost.

eg following program will print 1 not 0

    long number = 499999999000000001L;
    double converted = (double) number;
    System.out.println( number - (long) converted);

Answer 4

Are you looking for the binary conversion?

double result = Double.longBitsToDouble(15552451L);

This will give you the double with the same bit pattern as the long literal.

Binary or hexadecimal literals will come in handy, here. Here are some examples.

double nan = Double.longBitsToDouble(0xfff0000000000001L);
double positiveInfinity = Double.longBitsToDouble(0x7ff0000000000000L);
double positiveInfinity = Double.longBitsToDouble(0xfff0000000000000L);

(See Double.longBitsToDouble(long) )

You also can get the long back with

long bits = Double.doubleToRawLongBits(Double.NaN);

(See Double.doubleToRawLongBits(double) )

Answer 5

Long i = 1000000;
String s = i + "";
Double d = Double.parseDouble(s);
Float f = Float.parseFloat(s);

This way we can convert Long type to Double or Float or Int without any problem because it's easy to convert string value to Double or Float or Int.

Answer 6

You can try something like this:

long x = somevalue;

double y = Double.longBitsToDouble(x);

Answer 7

What do you mean by a long date type?

You can cast a long to a double:

double d = (double) 15552451L;

Answer 8

I think it is good for you.

BigDecimal.valueOf([LONG_VALUE]).doubleValue()

How about this code? :D