SHIFT OPERATORS

Bitwise Shift Operators

Three kinds of shift operators are present in Java namely Bitwise Left shift operator (<<), Bitwise right shift operator (>>) and Bitwise left shift with zero extension operator (>>>). If you want to know more about the precedence of operators, you can CHECK HERE.

Precedence	Operator	Type	Associativity
10	<<	Bitwise left shift	Left to Right
	>>	Bitwise right shift
	>>>	Bitwise right shift with zero extension

Java code to perform Bitwise left shift operation

The format for using bitwise left shift operator is: a<<b where ‘a’ is the number and ‘b’ represents how many times the number ‘a’ has to be shifted.

Eg) 7<<1

Here, 7 is a decimal number which is first converted into its binary equivalent.

7 – 0000 0111

Since b=1,

Each digit in 7’s binary equivalent is shifted once towards the left side. Thus the output becomes, 0000 1110 which is equivalent to 14. This operation can be implemented in Java as follows,

class operator{
    public static void main(String args[]){
        // Assigning value of x as 7
        byte x=7;
        //Performing left shift operation
        System.out.println("Bitwise Left Shift: 7<<1 = "+(x<<1));
        System.out.println("Bitwise Left Shift: 7<<7 = "+(x<<7));
    }
}

Output

Java code to perform Bitwise right shift operation

The syntax for performing bitwise right shift operation is a >> b and similar to the left shift operation, the number ‘a’ is shifted towards the right by ‘b’ times. Taking the example of 7 >> 1:

7 – 0000 0111

The right shift of ‘7’ by one bit results in 0000 0011 which is equivalent to 3.

Maximum number of shifts in Java

The maximum number of shifts which can occur in Java is 32 and when user gives the value of b greater than 32, the following happens:

Eg) 7 >> 33

The binary equivalent of 33 is 0010 0001. Whenever b> 32, only the last 5 digits of the binary equivalent of ‘b’ is taken. In this case, the last 5 bits are 0 0001. So the number 7 is shifted once towards the right. Hence the resultant is 0000 0011 which is equivalent to 3.

Right shift operation of a negative number

In case of negative numbers, the shifting operation is done in a different manner.

Eg) -7 >> 1

Step 1: The 2’s complement of the number ‘a’ is taken

The equivalent binary value of 7 is 0000 0111

2’s complement = 1’s complement + 1

1’s complement if taken by substituting all 1’s with 0’s and vice versa. Hence, the 1’s complement of 7 is 1111 1000. For taking 2’s complement, add 1 with the 1’s complement.

1111 1000

1 +

1111 1001

Step 2: The shifting operation is then done using the 2’s complement. While shifting, the Most Significant Bit (MSB) should be filled with 1.

Since ‘b’ value is 1, the result obtained in Step 1 is shifted by 1 and the MSB is filled with 1. The resultant is 1111 1100

Step 3: Take 2’s complement of the resultant which is the answer for the right shift operation of a negative number. Now, taking 2’s complement of the resultant 1111 1100, we get:

1’s complement of 1111 1101 = 0000 0011

Adding 1 to 1’s complement = 0000 0100

The value of -7 >> 1 is -4

class operator{

    public static void main(String args[]){

        // Assigning value of x as 7

        byte x=7;

        //Performing right shift operation

        System.out.println("Bitwise right Shift: 7>>1 = "+(x>>1));

        System.out.println("Bitwise right shift: 7>>33 = "+(x>>33));

        System.out.println("Bitwise right shift: -7>>1 = "+(-x>>1));

    }

}

Output

Java code to implement Bitwise right shift with zero extension

Bitwise right shift with zero extension (>>>) format is a >>> b and for positive number, the operation is same as a >> b. But, for negative numbers instead of substituting 1’s step 2, 0 is substituted. This operator returns an unsigned 32 bit integer and the following code provides the difference between the right shift and right shift with extension operators.

class operator{

    public static void main(String args[]){

        // Assigning value of x as 7

        byte x=7;

        // Positive values

        //Performing right shift operation

        System.out.println("Bitwise right Shift: 7>>11 = "+(x>>>11));

        //Performing right shift operation with zero extension

        System.out.println("Bitwise right shift with zero extension: 7>>>11 = "+(x>>11));

        // Negative input

        //Performing right shift operation

        System.out.println("Bitwise right shift: -7>>11 = "+(-x>>11));

        //Performing right shift operation with zero extension

        System.out.println("Bitwise right shift with zero extension: -7>>>11 = "+(-x>>>11));

    }

}

Output

From this output, it can be clearly visualized that the 1^st 2 outputs are same, since the input is positive. Changes occur in both the operators only when implementing negative numbers.