在Java中将十六进制数据读入字节数组中？ [英] Reading hexadecimal data into byte array in Java?

问题描述

我正在使用Java从SNES ROM读取数据。我打开一个流并将字节读入一个数组中：

  InputStream stream = open（foo.rom）; 
 final int startingSize = stream.available（）; 
 byte [] data = new byte [startingSize]; 
 final int numberRead = stream.read（data，0，startingSize）; 
  

在ROM中，我有这个值：

E4 2B 00 02 03 00 FF 3A 00 83

228 43 0 2 3 0 255 58 0 131（十进制）

然而，我的代码行为怪异。在设置了一些调试语句之后，当使用String.valueOf（data [ref]）打印时，我有这个模式：

-28 43 0 2 3 0 - 1 58 0 -125

（ROM中的这个地址是数据出现的第一个地址，但我注意到程序中其他地方的值不正确。）

尽我所能地告诉我的Java字节数组并不尊重十六进制数据。我怎样才能设置我的字节数组呢？

解决方案

Java将所有字节视为签名，因此它们只能处于范围-128至+127。位模式 E4 对应于二进制补码中的-28。

您可以将带符号字节转换为pretend-unsigned-通过执行类似于 String.valueOf（data [ref]& 0x00FF）的整数。这将剥离符号位并自动转换为int。

I'm reading data from an SNES ROM using Java. I am opening a stream and reading in the bytes into an array:

InputStream stream = open("foo.rom");
final int startingSize = stream.available();
byte[] data = new byte[startingSize];
final int numberRead = stream.read(data, 0, startingSize);

In the ROM, I have this value:

E4 2B 00 02 03 00 FF 3A 00 83

228 43 0 2 3 0 255 58 0 131 (in decimal)

However, my code is behaving weirdly. After setting up some debug statements, I have this pattern when printing with String.valueOf(data[ref]):

-28 43 0 2 3 0 -1 58 0 -125

(This address in the ROM is the first where data appears, but I am noticing incorrect values elsewhere in the program.)

As near as I can tell my Java byte array is not respecting the hexadecimal data. How can I set my byte array to do so?

解决方案

Java treats all bytes as being signed, so they can only be in the range -128 to +127. The bit pattern E4 corresponds to -28 in two's complement.

You can convert signed bytes to pretend-unsigned-ints by doing something like String.valueOf(data[ref] & 0x00FF). That will strip off the sign bit and auto-convert to an int.

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