javabigdecimal存储,JavaBigDecimal内存使用情况？

Is there a guideline for estimating the amount of memory consumed by a BigDecimal?

Looking for something similar to these guidelines for estimating String memory usage.

解决方案

If you look at the fields in the source for BigDecimal there is:

BigDecimal:

long intCompact &＃43;8 bytes

int precision &＃43;4 bytes

int scale &＃43;4 bytes

String stringCache &＃43;?

BigInteger intVal &＃43;?

BigInteger:

int bitCount &＃43;4 bytes

int bitLength &＃43;4 bytes

int firstNonzeroIntNum &＃43;4 bytes

int lowestSetBit &＃43;4 bytes

int signum &＃43;4 bytes

int[] mag &＃43;?

The comment for stringCache is "Used to store the canonical string representation, if computed.", so assuming that you don&＃39;t call toString we will leave that as zero bytes, so in total there are (8&＃43;4&＃43;4)&＃61;16 bytes &＃43; BigInteger in BigDecimal and 4&＃43;4&＃43;4&＃43;4&＃43;4&＃61;20 bytes &＃43; mag for BigInteger. So a total of 36 bytes plus the magnitude. As far as I can tell magnitude is always the minimum number of bits necessary to represent the full integer, so for a number n it will need log2(n) bits, which can be converted to ints. So in general you should be using about:

36 &＃43; Ceiling(log2(n)/8.0) bytes

(note this doesn&＃39;t include any of the other object descriptor overhead as your example link for strings does, but it should give you a good general idea.)