kabra.dabar kabra.dabar - 3 months ago 8
Java Question

Accuracy of double precision multiplication in java?

What is the guaranteed accuracy of multiplication operator for double values in java?

For example, 2.2 * 100 is 220.00000000000003, but 220 is a double number. 220.00000000000003 is the next double after 220.

Answer

The multiplication is working fine, but 2.2 cannot be represented exactly as a double. The closest doubles are:

  • 2.199999999999999733 (0x4001999999999999)
  • 2.200000000000000177 (0x400199999999999a)

Some software will print the latter value as 2.2, but that doesn't mean it's exact. It just means it's treated as "close enough".