Write a method called isOdd() in a class called OddTest, which takes an int as an argument and returns true if the int is odd

Question

I'm in my first year of Java and am having trouble with with a boolean method to test if even or odd. I have most of the code, but when I enter an odd number it returns it as even. My professor gave us the signature of the method: public static boolean isOdd(int number)

package homeWork1;
import java.util.Scanner;

public class OddTest {

   public static void main(String args[])
   {
      int number;
      System.out.println("Enter an integer to check if it is odd or even: ");
      Scanner input = new Scanner(System.in);
      number = input.nextInt();
      isOdd(number);

      boolean answer=isOdd(number);
      if (answer=true)
      {
          System.out.println("EVEN");
      }

      if (answer=false)
      {
          System.out.println("ODD");
      }



   }
   public static boolean isOdd(int number)
   { 
    if(number % 2 == 0)
   {
        return true;
    }
    return false;

}

If it is `%2 == 0` that means it is even... So instead `return false` if that statement is true. else `return true` something like this... `if( (number%2) == 0) { return true;} else {return false;}` — 3kings, Sep 10 '16 at 00:33
@James, please mark one of the answers to your question as accepted. — Jezor, Nov 01 '16 at 01:12

Jezor · Answer 1 · 2016-09-10T00:43:13.863

4

if (number % 2 == 0) means that the number is divisible by 2, and therefore it is even.

You want to change your condition to:

if (number % 2 != 0)

And, as a conditional statement is a boolean value, you can simplify it further like:

public static boolean isOdd(int number)
    return number % 2 != 0;
}

Also, you have an error in the code that uses your method.

  boolean answer=isOdd(number);
  if (answer=true)
  {
      System.out.println("ODD");
  }

  if (answer=false)
  {
      System.out.println("EVEN");
  }

Here, answer=true is an assignment, not comparison. You can fix it by writing:

if (isOdd(number))
{
    System.out.println("ODD");
}

else
{
    System.out.println("EVEN");
}

edited Sep 10 '16 at 00:43

answered Sep 10 '16 at 00:35

Jezor

3,253
2
19
43

better to use (number&1)==1 . Try isOdd(0x80000000) – ddyer Sep 10 '16 at 00:59
3

@ddyer I should like to challlenge that. `number % 2 != 0` is much more readable, which should always be your first choice. Besides, I see no other advantage in `(number & 1) == 1`. – Ole V.V. Sep 10 '16 at 01:24
number&1 is much faster. 1 cycle on most machines vs many cycles for division with remainder. Handwave about pipelining and smart compilers may help you though. The other thing is that the division may throw a number exception if the dividend is 0x80000000. – ddyer Sep 10 '16 at 09:27
@ddyer it will work [only with powers of 2](http://stackoverflow.com/a/3072710/5922757). As the OP seems to be a beginner programmer, it might make him only more confused about what's going on. Also, JVM is smart, I think it can optimize it out by itself. – Jezor Sep 11 '16 at 15:30

score 0 · Answer 2 · answered Sep 10 '16 at 00:34

0

Instead of checking whether answer is true or false, you're assigning these values. Checking for equality is == in Java. By the way, I'd recommend using just if (answer) and if (!answer) for booleans - looks simpler and less room for a mistake :)

answered Sep 10 '16 at 00:34

Roman Kotenko

489
7
16

Thanks for the help, everything works properly now. Tired eyes didn't catch the == – James Seeley Sep 10 '16 at 00:38
2

@JamesSeeley you might also want to rename *isOdd* method to *isEven* (or invert the return values and corresponding checks) as it's doing the opposite – Roman Kotenko Sep 10 '16 at 00:42

Write a method called isOdd() in a class called OddTest, which takes an int as an argument and returns true if the int is odd

2 Answers2