java中2的十六进制数到十进制的补码

发布于 2024-11-24 02:43:03 字数 246 浏览 2 评论 0原文

我有一个表示 2 的补码数的十六进制字符串。有没有一种简单的方法（库/函数）可以将十六进制转换为十进制而不直接使用其位？

EG 这是左边十六进制的预期输出：

"0000" => 0
"7FFF" => 32767 (max positive number)
"8000" => -32768 (max negative number)
"FFFF" => -1

谢谢！

原文

I have a hex string that represents a 2's complement number. Is there an easy way (libraries/functions) to translate the hex into a decimal without working directly with its bits??

E.G. This is the expected output given the hex on the left:

"0000" => 0
"7FFF" => 32767 (max positive number)
"8000" => -32768 (max negative number)
"FFFF" => -1

Thanks!

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

公布 2024-12-01 02:43:03

这似乎欺骗java转换数字而不强制得到正结果：

Integer.valueOf("FFFF",16).shortValue(); // evaluates to -1 (short)

当然这种事情只适用于8、16、32和64位2的补码：

Short.valueOf("FF",16).byteValue(); // -1 (byte)
Integer.valueOf("FFFF",16).shortValue(); // -1 (short)
Long.valueOf("FFFFFFFF",16).intValue(); // -1 (int)
new BigInteger("FFFFFFFFFFFFFFFF",16).longValue(); // -1 (long)

示例如下。

This seems to trick java into converting the number without forcing a positive result:

Integer.valueOf("FFFF",16).shortValue(); // evaluates to -1 (short)

Of course this sort of thing only works for 8, 16, 32, and 64-bit 2's complement:

Short.valueOf("FF",16).byteValue(); // -1 (byte)
Integer.valueOf("FFFF",16).shortValue(); // -1 (short)
Long.valueOf("FFFFFFFF",16).intValue(); // -1 (int)
new BigInteger("FFFFFFFFFFFFFFFF",16).longValue(); // -1 (long)

Example here.

回复收藏 0 原文

甜扑 2024-12-01 02:43:03

只需编写一个实用方法：

 public static Integer twosComp(String str) throws java.lang.Exception {
       Integer num = Integer.valueOf(str, 16);
       return (num > 32767) ? num - 65536 : num;
 }

测试：

 twosComp("7FFF") -> 32767
 twosComp("8000") -> -32768
 twosComp("FFFF") -> -1

Just write a utility method:

 public static Integer twosComp(String str) throws java.lang.Exception {
       Integer num = Integer.valueOf(str, 16);
       return (num > 32767) ? num - 65536 : num;
 }

Tests:

 twosComp("7FFF") -> 32767
 twosComp("8000") -> -32768
 twosComp("FFFF") -> -1

回复收藏 0 原文

青巷忧颜 2024-12-01 02:43:03

这似乎运作得相当不错。它可以通过传递非标准长度字符串来欺骗它：“FFF”映射到-1。零填充将纠正错误。

您不清楚您想要什么类型的返回，所以我返回了 Number，无论大小合适。

public Number hexToDec(String hex)  {
   if (hex == null) {
      throw new NullPointerException("hexToDec: hex String is null.");
   }

   // You may want to do something different with the empty string.
   if (hex.equals("")) { return Byte.valueOf("0"); }

   // If you want to pad "FFF" to "0FFF" do it here.

   hex = hex.toUpperCase();

   // Check if high bit is set.
   boolean isNegative =
      hex.startsWith("8") || hex.startsWith("9") ||
      hex.startsWith("A") || hex.startsWith("B") ||
      hex.startsWith("C") || hex.startsWith("D") ||
      hex.startsWith("E") || hex.startsWith("F");

   BigInteger temp;

   if (isNegative) {
      // Negative number
      temp = new BigInteger(hex, 16);
      BigInteger subtrahend = BigInteger.ONE.shiftLeft(hex.length() * 4);
      temp = temp.subtract(subtrahend);
   } else {
      // Positive number
      temp = new BigInteger(hex, 16);
   }

   // Cut BigInteger down to size.
   if (hex.length() <= 2) { return (Byte)temp.byteValue(); }
   if (hex.length() <= 4) { return (Short)temp.shortValue(); }
   if (hex.length() <= 8) { return (Integer)temp.intValue(); }
   if (hex.length() <= 16) { return (Long)temp.longValue(); }
   return temp;
}

示例输出：

"33" -> 51
"FB" -> -5
"3333" -> 13107
"FFFC" -> -4
"33333333" -> 53687091
"FFFFFFFD" -> -3
"3333333333333333" -> 3689348814741910323
"FFFFFFFFFFFFFFFE" -> -2
"33333333333333333333" -> 241785163922925834941235
"FFFFFFFFFFFFFFFFFFFF" -> -1

This seems to work reasonably well. It can be fooled by passing it non-standard length strings: "FFF" maps to -1. Zero padding will correct the fault.

You are not clear on what type return you want, so I have returned Number, at whatever size is appropriate.

public Number hexToDec(String hex)  {
   if (hex == null) {
      throw new NullPointerException("hexToDec: hex String is null.");
   }

   // You may want to do something different with the empty string.
   if (hex.equals("")) { return Byte.valueOf("0"); }

   // If you want to pad "FFF" to "0FFF" do it here.

   hex = hex.toUpperCase();

   // Check if high bit is set.
   boolean isNegative =
      hex.startsWith("8") || hex.startsWith("9") ||
      hex.startsWith("A") || hex.startsWith("B") ||
      hex.startsWith("C") || hex.startsWith("D") ||
      hex.startsWith("E") || hex.startsWith("F");

   BigInteger temp;

   if (isNegative) {
      // Negative number
      temp = new BigInteger(hex, 16);
      BigInteger subtrahend = BigInteger.ONE.shiftLeft(hex.length() * 4);
      temp = temp.subtract(subtrahend);
   } else {
      // Positive number
      temp = new BigInteger(hex, 16);
   }

   // Cut BigInteger down to size.
   if (hex.length() <= 2) { return (Byte)temp.byteValue(); }
   if (hex.length() <= 4) { return (Short)temp.shortValue(); }
   if (hex.length() <= 8) { return (Integer)temp.intValue(); }
   if (hex.length() <= 16) { return (Long)temp.longValue(); }
   return temp;
}

Sample output:

"33" -> 51
"FB" -> -5
"3333" -> 13107
"FFFC" -> -4
"33333333" -> 53687091
"FFFFFFFD" -> -3
"3333333333333333" -> 3689348814741910323
"FFFFFFFFFFFFFFFE" -> -2
"33333333333333333333" -> 241785163922925834941235
"FFFFFFFFFFFFFFFFFFFF" -> -1

回复收藏 0 原文

~没有更多了~