Detailed introduction to bitwise operators and shift operations in Java

1. Bit operations

There are 4 bit operations in Java. Their operation rules are as follows:

(1) Bitwise AND (&): both two bits are 1, the result is 1, otherwise it is 0;

( 2) Bitwise OR (|): If one of the two bits is 1, the result is 1, otherwise it is 0;

(3) Bitwise negation (~): 0 becomes 1, 1 becomes 0;

(4 ) bitwise XOR (^): two bits, if they are the same, the result is 0; if they are different, the result is 1;

Note:

(1) The sign bit (highest bit) in the bit operation also changes;

(2) Bitwise operators are somewhat similar to logical operators (logical AND &&, logical OR ||, logical NOT!). However, logical operators can only operate on boolean variables

(that is, the values ​​on the left and right sides are boolean values);

2. Bit operation application

(1) ~5 = ?

a) 5’s complement The code is:

00000000 00000000 00000000 00000101

b) The bitwise negation (~) of 5 is:

11111111 11111111 11111111 11111010

Note: Because the high digit is 1 (negative number), the complement must be Convert to the original code; if the high digit is 0 (positive number), there is no need to convert the complement to the original code, because the original code, complement and complement of the positive number are the same.

c) Convert the complement of the negative number to the complement:

11111111 11111111 11111111 11111001

d) Convert the complement of the negative number to the original code:

10000000 00000000 00000 000 00000110

e) will binary The original code is converted to decimal:

10000000 00000000 00000000 00000110 = 0 * 2^0 + 1 * 2^1 + 1 * 2^2 = 0+2+4 = -6 (the highest bit is 1, so it is a negative number)

3. Shift operation:

There are 3 shift operators in Java.

(1) Arithmetic right shift (>>): The low bit overflows, the sign bit remains unchanged, and the overflowed high bit is filled with the sign bit;

For example: a >> b: a is the number to be moved, b is the number of digits to be moved, the same applies to the following;

(2) Arithmetic left shift (<< ): The sign bit remains unchanged, and the low bit is filled with 0;

(3) Logical right shift (>> ;>): The low bit overflows, and the high bit is filled with 0; Note: The sign bit (highest bit) in the logical right shift (>>>) also changes;

IV. Note:

bit operations and shifts Bit operations all use binary complement to perform operations, so avoid!

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