Core Java: Bit-Shift Operator

Bit-shift operators perform left or right shift on an operand by a specified number of bits. Right-shift can be either signed-extended (>>) (padded with signed bit) or unsigned-extended (>>>) (padded with zeros). Left-shift is always padded with zeros (for both signed and unsigned).

 

Operator	Usage	Description
<<	operand << number	Left-shift and padded with zeros
>>	operand >> number	Right-shift and padded with sign bit (signed-extended right-shift)
>>>	operand >>> number	Right-shift and padded with zeros (unsigned-extended right-shift)

 

Example

 

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public class BitShiftTest {    public static void main(String[] args) {       int x = 0xAAAA5555;               // a negative number (sign bit (msb) = 1)       int y = 0x55551111;               // a positive number (sign bit (msb) = 0)       System.out.printf("%d%n", x);     // -1431677611       System.out.printf("%d%n", y);     // 1431638289       System.out.printf("%08X%n", x<<1);  // 5554AAAAH       System.out.printf("%08X%n", x>>1);  // D5552AAAH       System.out.printf("%d%n", x>>1);    // negative       System.out.printf("%08X%n", y>>1);  // 2AAA8888H       System.out.printf("%08d%n", y>>1);  // positive       System.out.printf("%08X%n", x>>>1); // 55552AAAH       System.out.printf("%d%n", x>>>1);   // positive       System.out.printf("%08X%n", y>>>1); // 2AAA8888       System.out.printf("%d%n", y>>>1);   // positive       // More efficient to use signed-right-right to perform division by 2, 4, 8,...       int i1 = 12345;       System.out.println("i1 divides by 2 is " + (i1 >> 1));       System.out.println("i1 divides by 4 is " + (i1 >> 2));       System.out.println("i1 divides by 8 is " + (i1 >> 3));       int i2 = -12345;       System.out.println("i2 divides by 2 is " + (i2 >> 1));       System.out.println("i2 divides by 4 is " + (i2 >> 2));       System.out.println("i2 divides by 8 is " + (i2 >> 3));    } }

  Types and Bitwise Operations

 

The bitwise operators are applicable to integral primitive types: byte, short, int, long and char. char is treated as unsigned 16-bit integer. There are not applicable to float and double. The '&', '|', '^', when apply to two booleans, perform logical operations. Bit-shift operators are not applicable to booleans.

Like binary arithmetic operations:

 

·        byte, short and char operands are first promoted to int.

 

·        If both the operands are of the same type (int or long), they are evaluated in that type and returns a result of that type.

 

·        If the operands are of different types, the smaller operand (int) is promoted to the larger one (long). It then operates on the larger type (long) and returns a result in the larger type (long).