After Java Puzzlers.

class Test {

    public boolean isOddWrong1(int i) {
        // -1 % 2 returns not 1 but -1
        return i % 2 == 1;
    }

    public boolean isOddCorrect1(int i) {
        // Get a new angle on test
        return i % 2 != 0;
    }

    public boolean isOddCorrect2(int i) {
        // the best
        return (i & 1) != 0;
    }

    public static void main(String[] args) {

        Test t = new Test();
        System.out.println("isOddWrong1(-1)=" + t.isOddWrong1(-1));
        System.out.println("isOddCorrect1(-1)=" + t.isOddCorrect1(-1));
        System.out.println("isOddCorrect2(-1)=" + t.isOddCorrect2(-1));
    }
}