我看一个有名的开源组件，用到byte--->char代码是这样的:
c[i] = (char) (b[i] & 0xff) （b[i]为byte型，c[i]为char型)
觉得与一下0xff没什么用。直接c[i] = (char)b[i]有何异？
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避免java隐含的符号扩展吧
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因为byte的取值范围是 -128～127，而Char是0～65535
所以需要& 0xFF 使得byte原来的负值变成正的
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- Java code
0xFF is hexidecimal, you can Wikipedia that part. FF is a representation of 00000000 00000000 00000000 11111111(a 32-bit integer)& means bit-wise "and", and so when you use it on two ints, each pair of bits from those two ints is and-ed and the result is placed in the resultant int:Example (showing 16 bits only)0101 1100 1010 1100&0000 0000 1111 1111-----------------=0000 0000 1010 1100So as you can see, 0xFF is often used to to isolate a byte in an integer, by truncating the integer to one byte's worth of 1's.For more information, see this WP article:
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与 0xff 做 & 运算会将 byte 值变成 int 类型的值，也将 -128～0 间的负值都转成正值了。
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- Java code
char c = (char)-1 & 0xFF;char d = (char)-1;System.out.println((int)c);System.out.println((int)d);
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1) 位运算不限制为int, long也行的。
2)
3) 负数进行&操作时需要转成补码，-2 的补码是0xFFFFFFFE