Java BigDecimal 内存使用情况？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/2501176/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Java BigDecimal memory usage?
提问by Marcus Leon
Is there a guideline for estimating the amount of memory consumed by a BigDecimal?
是否有用于估计 a 消耗的内存量的指南BigDecimal？
Looking for something similar to these guidelinesfor estimating Stringmemory usage.
寻找类似于这些用于估计内存使用情况的指南String。
回答by M. Jessup
If you look at the fields in the source for BigDecimalthere is:
如果您查看源中的字段，则BigDecimal有：
BigDecimal:
long intCompact +8 bytes
int precision +4 bytes
int scale +4 bytes
String stringCache +?
BigInteger intVal +?
BigInteger:
int bitCount +4 bytes
int bitLength +4 bytes
int firstNonzeroIntNum +4 bytes
int lowestSetBit +4 bytes
int signum +4 bytes
int[] mag +?
The comment for stringCachesays
评论stringCache说
Used to store the canonical string representation, if computed.
用于存储规范字符串表示（如果已计算）。
Assuming you don't call .toString(), it will remain zero bytes. Hence BigDecimalis (8+4+4)=16 bytes + BigInteger.
假设您不调用.toString()，它将保持零字节。因此BigDecimal是 (8+4+4)=16 bytes + BigInteger。
BigIntegeritself is 4+4+4+4+4=20 bytes + mag.
BigInteger本身是 4+4+4+4+4=20 bytes + mag。
20+16 gives total of 36 bytes plus the magnitude, which is always the minimum number of bits necessary to represent the full integer. For a number nit will need log2(n)bits, which can be converted to ints. You should be using about:
20+16 总共有 36 个字节加上幅度，这始终是表示完整整数所需的最小位数。对于一个数字，n它需要log2(n)位，可以转换为整数。你应该使用关于：
36 + Ceiling(log2(n)/8.0) bytes
(note this doesn'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.)
（请注意，这不包括任何其他对象描述符开销，如您的字符串示例链接所做的那样，但它应该给您一个很好的总体思路。）
回答by Adamski
If you dig into the internals of BigDecimalyou'll see that it uses a compact representation if the significand is <= Long.MAX_VALUE. Hence, the memory usage can vary depending on the actual values you're representing.
如果您深入研究内部结构，BigDecimal您会发现如果有效数是 <= 则它使用紧凑表示Long.MAX_VALUE。因此，内存使用量可能会因您所代表的实际值而异。
