Left Shift Operator in Java

The decimal representation of a number is a base-10 number system having only ten states 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. For example, 4, 10, 16, etc.

The Binary representation of a number is a base-2 number system having only two states 0 and 1. For example, the binary representation of 4, a base-9 decimal number system is given by 100, 10 as 1010, 16 as 1000, etc.

Left Shift

The left shift means that shift each of the bits is in binary representation toward the left.

Logical Left Shift

For example, when we say left shift 5 or 101 by one position. We will shift each of the bits by one position towards the left. So after shifting the number 5 towards the left by one position, the number obtained is 10 or 1010. Now let us again left shift 10 by two positions. Again, we will shift each of the bits by two positions towards the left. The number obtained is 40 or 101000.

Note: Left shifting a number by certain positions is equivalent to multiplying the number by two raised to the power of the specified positions. That is,

left shift x by n positions <=> x * 2n 

Left Shift Operator in Java

Most of the languages provide left shift operators using which we can left shift a number by certain positions and Java is one of them. The syntax of the left-shift operator in Java is given below,

Syntax:

x << n

Here,
x: an integer
n: a non-negative integer 

Return type: An integer after shifting x by n positions toward left

Exception: When n is negative the output is undefined

Below is the program to illustrate how we can use the left shift operator in Java.

Example 1:

Java

// Java program to illustrate the
// working of left shift operator

import java.io.*;

class GFG {

      // Main method
    public static void main (String[] args) {

        // Number to be shifted
        int x = 5;

        // Number of positions
        int n = 1;

        // Shifting x by n positions towards left using left shift operator
        int answer = x << n;

        // Print the number obtained after shifting x by n positions towards left
        System.out.println("Left shift " + x + " by " + n + " positions : " + answer);

        // Number to be shifted
        x = answer;

        // Number of positions
        n = 2;

        // Shifting x by n positions towards left using left shift operator
        answer = answer << n;

        // Print the number obtained after shifting x by n positions towards left
        System.out.println("Left shift " + x + " by " + n + " positions : " + answer);

    }
}

Output

Left shift 5 by 1 positions : 10
Left shift 10 by 2 positions : 40

Example 2:

Java

// Java program to illustrate the
// working of left shift operator

import java.io.*;

class GFG {

      // Main method
    public static void main (String[] args) {

        // Number to be shifted
        int x = -2;

        // Number of positions
        int n = 1;

        // Shifting x by n positions towards
        // left using left shift operator
        int answer = x << n;

        // Print the number obtained after shifting x by n positions towards left
        System.out.println("Left shift " + x + " by " + n + " positions : " + answer);

        // Number to be shifted
        x = answer;

        // Number of positions
        n = 2;

        // Shifting x by n positions towards
        // left using left shift operator
        answer = answer << n;

        // Print the number obtained after shifting x by n positions towards left
        System.out.println("Left shift " + x + " by " + n + " positions : " + answer);

    }
}

Output

Left shift -2 by 1 positions : -4
Left shift -4 by 2 positions : -16

Time complexity: O(1)

Space complexity: O(1)

Note: For arithmetic left shift, since filling the right-most vacant bits with 0s will not affect the sign of the number, the vacant bits will always be filled with 0s, and the sign bit is not considered. Thus, it behaves in a way identical to the logical (unsigned) left shift. So there is no need for a separate unsigned left sift operator.