Java: How to Count odd Integers?

[Tocsin_786]

This has been puzzling me for a month. All my HW is due on codelab and so it has to be very specific in what its asking. I dont conceptually understand how I can have a user input a number, and then have Java count up or down to the next odd number... or just count in odds or even in general. The code I have provided is from Chegg, but they failed to explain anything, and so I'm lost. 

* keep in mind, I can't use arrays, or if statements because we havent learned that yet.*

 

Heres the code so you can copy and paste. 

import java.util.Scanner;
public class OddPredecessor {
	public static void main(String [] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		System.out.println((n-1 % 2==1) ? n -1 : n -2);
	}
}

 

 

 

 

 

[Cela1]

In Java (and many other languages) % is the modulo operator (you can think of it like a remainder operator - except it does things slightly differently with negative numbers).  The '?'  is a ternary operator, meaning that if the modulo operation is true it will select the second (n-2) branch, otherwise it will select the (n-1) branch.

 

Edit: Specifically 'n' is being read as the next integer (IDK why they are doing it like that), so 'n-1' represents the number you typed in. Using modulo 2, if you type in an even number you get 0 (even - first) out, so it subtracts one to get the last odd number,. Otherwise that number will be even, so we subtract 2 to get the last even number.

 

Hope this helps. Feel free to ask more if it doesn't.

[Tocsin_786]

6 minutes ago, Cela1 said:

In Java (and many other languages) % is the modulo operator (you can think of it like a remainder operator - except it does things slightly differently with negative numbers).  The '?'  is a ternary operator, meaning that if the modulo operation is true it will select the second (n-2) branch, otherwise it will select the (n-1) branch.

Yea its a conditional statement, kinda like an If statement but condensed. So in this case the n input is either being subtracted or added by either 1 or 2. How would I change it so it does it in intervals automatically? like what if I want to count every second odd number or something like that? 

[Cela1]

32 minutes ago, Tocsin_786 said:

Yea its a conditional statement, kinda like an If statement but condensed. So in this case the n input is either being subtracted or added by either 1 or 2. How would I change it so it does it in intervals automatically? like what if I want to count every second odd number or something like that? 

I'm not *quite* sure what you mean, but if you change the -1 / -2 to a +3 / +5, then you should get the second odd number. If you actually want to count, then use a FOR loop like;

 

import java.util.Scanner;
public class OddPredecessor {
	public static void main(String [] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
                n = (n-1 % 2==1) ? n -1 : n -2
                for (int i = n; i < y; i+=2) {
                       System.out.println(n); 
                }
	}
}

 

Where 'y' is where you want to stop (can be written as n+a, where a is the amount over the selected digit that you want to show).