What does this boolean “(number & 1) == 0” mean?

Question

On CodeReview I posted a working piece of code and asked for tips to improve it. One I got was to use a boolean method to check if an ArrayList had an even number of indices

Answer 1

& is the bitwise AND operator. && is the logical AND operator

In binary, if the digits bit is set (i.e one), the number is odd.

In binary, if the digits bit is zero , the number is even.

(number & 1) is a bitwise AND test of the digits bit.

Another way to do this (and possibly less efficient but more understandable) is using the modulus operator %:

private static boolean isEven(int number)
{
    if (number < 0)
       throw new ArgumentOutOfRangeException();

    return (number % 2) == 0;
}

Answer 2

This is Logical design concept bitwise & (AND)operater.

return ( 2 & 1 ); means- convert the value to bitwise numbers and comapre the (AND) feature and returns the value.

Prefer this link http://www.roseindia.net/java/master-java/java-bitwise-and.shtml

Answer 3

Single & means bit-wise and operator not comparison

So this code checks if the first bit (least significant/most right) is set or not, which indicates if the number is odd or not; because all odd numbers will end with 1 in the least significant bit e.g. xxxxxxx1