Java：签名长到无符号长字符串 [英] Java: signed long to unsigned long string

问题描述

是否有一种简单快捷的方法将Java签名长转换为无符号长字符串？

Is there an easy and fast way to convert a Java signed long to an unsigned long string?

-1                    ->  "18446744073709551615"
-9223372036854775808  ->  "09223372036854775808"
 9223372036854775807  ->  "09223372036854775807"
 0                    ->  "00000000000000000000"

推荐答案

以下是使用BigInteger的解决方案：

Here is a solution using BigInteger:

/** the constant 2^64 */
private static final BigInteger TWO_64 = BigInteger.ONE.shiftLeft(64);

public String asUnsignedDecimalString(long l) {
   BigInteger b = BigInteger.valueOf(l);
   if(b.signum() < 0) {
      b = b.add(TWO_64);
   }
   return b.toString();
}

这是因为两个s中（带符号）的无符号值补码只比签名值大2 ^（位数），而Java的 long 有64位。

This works since the unsigned value of a (signed) number in two-s complement is just 2^{(number of bits)} more than the signed value, and Java's long has 64 bits.

BigInteger有这个很好的 toString（）方法，我们可以在这里使用。

And BigInteger has this nice toString() method which we can use here.

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