Java Byte shift Operation considerations

Java to byte +-*/>> >>> << & | ^ (add, subtract, multiply, divide, shift right, shift left, unsigned right, bit and, bit or, bitwise XOR) operations, will be the first to convert a byte to int, then the operation. This fact can lead to a variety of problems:

Suppose we want to do the following byte operation: 1111 1000 to the right 1 bits, then 0000 0001 or operation, 0111 1101. The intuitive writing procedure is as follows:byte B = 0xf8;byte B2 = b >> 1 | 0x01; There are multiple errors in this notation, which are now corrected individually: 1 compiler error, int cannot be converted directly to bytein order to solve this problem, strengthen the system transformation. byte B = (byte) 0xf8;byte b2 = (byte) ((b >> 1) | 0x01); 2 output is 1111 1101 not what we want. 0011 1101The reason is that >> is signed to the right, and when the sign bit is 1 o'clock, the left side is 1 instead of 0. Modify to use >>> unsigned right shift:byte B = (byte) 0xf8;byte b2 = (byte) ((b >>> 1) | 0x01);3 The output remains 1111 1101 after operationThe reason is that byte is converted to int before the operation, so the decomposition of the operation steps are as follows:Convert b to int 1111 1000 to 11111111 11111111 11111111 11111000unsigned Right shift 1-bit 01111111 11111111 11111111 11111100with 0x01 bitwise OR 01111111 11111111 11111111 11111101force conversion back to byte 11111101solution, precede the right-shift operation with 0xFFbyte B = (byte) 0xf8;byte b2 = (Byte) (((b & 0xff) >>> 1) | 0x01); Note that parentheses must be added because >>> has a higher priority than &4 after running the discovery output for the result we want 0111 1101. The operation steps are broken down as follows:Convert b to int 1111 1000 to 11111111 11111111 11111111 11111000& operation with 0xFF 00000000 00000000 00000000 11111000unsigned Right shift 1-bit 00000000 00000000 00000000 01111100with 0x01 bitwise OR 00000000 00000000 00000000 01111101force conversion back to byte 011111015 about System.out.println ();byte B = (byte) 0xf8;System.out.println (b); --The final output is-8The operation steps are:Convert b to int 1111 1000 to 11111111 11111111 11111111 11111000take sign bit- -1111111 11111111 11111111 11111000Take back +1 (because it is in complement) -0000000 00000000 00000000 00001000Output-8 Final Conclusion: 1 Distinguishing between >> and >>> 2 First & 0xFF before >> operation 3 Note the symbol priority, using parentheses correctly. 4 It is important to note that & 's priority is less than +. So the result of a = B & 0xFF + 2000 may not be what you want .Attached: a function to print byte,int each bit value. public static void Printbyte (Byte b) {for (int i = 7; I >=0; I-) {int shiftleft = (b >> i) & 0x01        ;    System.out.print (Shiftleft); } System.out.println ();}         public static void Printint (Int. b) {for (int i = +; I >=0; I-) {int shiftleft = (b >> i) & 0x01;    System.out.print (Shiftleft); } System.out.println ();}

Java Byte shift Operation considerations