如何将字节数组转换为其数值(Java)? [英] How to convert a byte array to its numeric value (Java)?

问题描述

我有一个 8 字节的数组，我想将其转换为相应的数值.

I have an 8 byte array and I want to convert it to its corresponding numeric value.

例如

byte[] by = new byte[8];  // the byte array is stored in 'by'

// CONVERSION OPERATION
// return the numeric value

我想要一个执行上述转换操作的方法.

I want a method that will perform the above conversion operation.

推荐答案

假设第一个字节是最低有效字节:

Assuming the first byte is the least significant byte:

long value = 0;
for (int i = 0; i < by.length; i++)
{
   value += ((long) by[i] & 0xffL) << (8 * i);
}

第一个字节是最重要的，然后有点不同:

Is the first byte the most significant, then it is a little bit different:

long value = 0;
for (int i = 0; i < by.length; i++)
{
   value = (value << 8) + (by[i] & 0xff);
}

用 BigInteger 替换 long，如果你有超过 8 个字节.

Replace long with BigInteger, if you have more than 8 bytes.

感谢 Aaron Digulla 纠正我的错误.

Thanks to Aaron Digulla for the correction of my errors.

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