Convert a Double to long without losing the exact value

Question

I have a Double object which loses the exact value when being converted to a long value.

Double d = 1.14*100
    
System.out.println(d.longValue());

The above statement would print: 113.

I want 114 to be printed.

Floating point numbers are not exact. Do you want to round first? — Tim S., Nov 08 '13 at 20:51
Be aware that what you think is the Double value 114 may actually be 113.99999999... internally, and your code ends up just truncating the decimal portion. As Tim S suggested, you need to incorporate rounding. — hatchet - done with SOverflow, Nov 08 '13 at 20:51
If you want to prevent your code from loosing precision you probably should use `BigDecimal`. — Pshemo, Nov 08 '13 at 20:51
Duplicate: http://stackoverflow.com/questions/321549/double-to-long-conversion — Tarik, Nov 08 '13 at 20:55
Agreed with @Pshemo -- unless there's some good compelling reason to use `Double`, you'd be much better off with `BigDecimal`. — Reinstate Monica -- notmaynard, Nov 08 '13 at 20:56

Donvino · Accepted Answer · 2013-11-09T17:30:54.003

7

If you need the exact 114 value you ned to use Math.round:

double d = 1.14*100;
System.out.println(Math.round(d));

edited Nov 09 '13 at 17:30

answered Nov 08 '13 at 20:55

Donvino

score 4 · Answer 2 · answered Nov 08 '13 at 20:54

4

Try this

Long.parseLong( String.format( "%.0f",doublevalue ) ) ;

answered Nov 08 '13 at 20:54

Jans

score 3 · Answer 3 · edited Nov 08 '13 at 21:00

3

If you are looking for an integer / long value representation with the value you are expecting, you can use this:

Math.round(1.14 * 100)

edited Nov 08 '13 at 21:00

Chris Forrence

answered Nov 08 '13 at 20:54

user2871923

score 1 · Answer 4 · answered Nov 08 '13 at 20:52

1

Firstly, a double is not exact. Next, when casting a double/float to a long/int, the decimal part is dropped (not rounded).

To get the nearest value, you'll need to round it:

System.out.println(Math.round(d));

answered Nov 08 '13 at 20:52

Bohemian

4 Answers4