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Kollegah der Boss
Kollegah der Boss

Reputation: 61

Why Java isnt calculating logical shift right correctly?

I just learned about logical shift right. Why my java isnt calculating it correctly? Example:

public class Operators {

    public static void main(String[] args) {
        byte z = -16;
        System.out.println((z >>> 2));
    }    
}

Why Java output: 1073741820

-16 = 1111 0000
-16 >>> 2 = 0011 1100 = 60

Thanks for the help :)

Upvotes: 1

Views: 175

Answers (1)

Arvind Kumar Avinash
Arvind Kumar Avinash

Reputation: 79085

The unsigned right shift operator >>> do not use the sign bit to fill the trailing positions. It always fills the trailing positions by 0.

public class Main {
    public static void main(String[] args) {
        String s = "00000000000000000000000000000000";
        byte z = -16;
        System.out.println("z in decimal: " + z + ",              binary: " + s.substring(Integer.toBinaryString(z).length())
                + Integer.toBinaryString(z));
        System.out.println("z >>> 1 in decimal: " + (z >>> 1) + ", binary: "
                + s.substring(Integer.toBinaryString(z >>> 1).length()) + Integer.toBinaryString(z >>> 1));
        System.out.println("z >>> 2 in decimal: " + (z >>> 2) + ", binary: "
                + s.substring(Integer.toBinaryString(z >>> 2).length()) + Integer.toBinaryString(z >>> 2));
    }
}

Output:

z in decimal: -16,              binary: 11111111111111111111111111110000
z >>> 1 in decimal: 2147483640, binary: 01111111111111111111111111111000
z >>> 2 in decimal: 1073741820, binary: 00111111111111111111111111111100

Upvotes: 2

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