Java Interview Question: Determining Whether an Integer Is Odd – Discussion and Solutions

The article introduces a seemingly simple Java interview question: write a method public boolean isOdd(int i) that returns true if the given integer is odd.

Initial candidate answers use System.out.println statements or return statements based on i % 2 == 1, but they contain compilation errors or verbose logic.

Through a series of interview prompts, candidates are guided to improve the code, handling negative numbers and simplifying the expression to a single return statement:

public boolean isOdd(int i) {
    return i % 2 == 1;
}

Further discussion explores faster alternatives to the modulo operation, leading to bitwise approaches. One candidate suggests using shift operators, which is not ideal, and finally the optimal solution using a bitwise AND is presented:

public boolean isOdd(int i) {
    return (i & 1) == 1;
}

The article also notes that, contrary to intuition, the bitwise version does not show a measurable speed advantage over the modulo version in practical tests, prompting a deeper conversation about compiler optimizations and CPU behavior.