从整数创建一个字节 [英] Creating a byte from an integer

问题描述

我想用整数创建一个字节。例如，我有一个4的整数，我想创建一个值为4的字节。当我做的事情像

I want to create a byte using an integer. For example I have an integer of 4, I want to create a byte with a value of 4. When I do something like

byte test = 134;

我得到的字节值为-122，我希望字节值只有134，这样我才能稍后将此转换为ascii。

I get an byte value of -122 wheras I want a byte value of simply 134 so that i can convert this to ascii later on.

我不确定如何实现此目的，但欢迎任何可以提供的帮助。谢谢。

I am unsure of how to achieve this but would welcome any help that can be provided. Thanks.

推荐答案

在Java byte 中被解释为签名（沿着 int s， short s， long s） 。 134 的无符号字节值与 -122 的有符号字节值相当。如果您希望使用 byte 的无符号值，可以将此值存储在超过8位的有符号整数中，例如 int ：

In Java bytes are interpreted as signed (along with ints, shorts, and longs). The unsigned byte value of 134 is bit-equivalent to the signed byte value of -122. If you wish to use the unsigned value of a byte, you can do so by storing this value in a signed integer with more than 8 bits, such as an int:

byte test = (byte) 134;
int unsignedByteValue = ((int) test) & 0xff;
// now unsignedByteValue == 134

0xff的位掩码确保只有 unsignedByteValue 的低8位为1。否则，负签名的字节将导致签名扩展名为负$ signed c $ c> int 。

The bitmask of 0xff ensures that only the lower 8 bits of unsignedByteValue are ones. Otherwise, a negative signed byte would result in a negative signed int by sign extension.

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