我收到从int到boolean类型不匹配的错误

Question

The code is to check whether a number is even or odd using the last bit is 1 or 0. if last bit is 1 it will go in if and print odd

import java.util.Scanner;

public class Even_or_odd {
    public void Check_even_or_odd(int a) {
        if(a&1)//error:Type mismatch: cannot convert from int to boolean
            System.out.println("odd");
        else
            System.out.println("even");
   }
   public static void main(String[] args) {
        System.out.println("enter a number to check even or odd");
        Scanner scan=new Scanner(System.in);
        int a=scan.nextInt();
        scan.close();
        Even_or_odd e=new Even_or_odd();
        e.Check_even_or_odd(a);
    }
}

Answer 1

Your code tests a for being odd/even by masking its binary representation with 1 , which has all bits set to zero except least significant one, which is set to 1 .

Odd numbers will produce 1 when masked with 1 ; even numbers will produce zero. However, you cannot write if (1) or if (0) , because there is no implicit conversion from int to boolean in Java. You need to write

if ((a&1) != 0)

to fix this problem.

Answer 2

Instead of binary operations, which is what I guess you are trying to do, check the input value using modulo:

if (a % 2 == 0) {
  System.out.println("even");
} else {
  System.out.println("odd");
}

In the condition block of the if statement you have to have a boolean value or an expression that evaluates to a boolean. a&1 evaluates to an integer.

Also see Check whether number is even or odd