Thread: Coding a statement that increments from 20-40 (only in even numbers) - fall-thru switch

Hello all,

I need help comprehending a fall-thru switch and how to catch the odd numbers using the option in the switch.

Here is my code:


public class HolstienSFallThruSwitch

{
public static void main(String[] args)
{

for(int i=20; i<=40; i+=2)
{

switch (i)
{
}
System.out.println(i);
}
}
}


It prints only the even numbers incrementing by 2, starting with the number 20. How would one "catch" the odd numbers in the switch? Thank you!

Hello all,

I need help comprehending a fall-thru switch that would increment 20-40 using even numbers, and how to catch the odd numbers using the option in the switch.

Here is my code:


public class HolstienSFallThruSwitch

{
public static void main(String[] args)
{

for(int i=20; i<=40; i+=2)
{

switch (i)
{
}
System.out.println(i);
}
}
}


It prints only the even numbers incrementing by 2, starting with the number 20. How would one "catch" the odd numbers in the switch? Thank you!

Perhaps you mean something like:

public class FallThroughSwitch {
 
    public static void main(String[] args) {
 
        for (int i = 20; i <= 40; i++) {
            switch (i) {
                case 21:
                case 23:
                case 25:
                case 27:
                case 29:
                case 31:
                case 33:
                case 35:
                case 37:
                case 39:
                    break;
                default:
                    System.out.println(i);
                    break;
            }
        }
    }
}

With the +1 increments, the odd-numbered cases will fall through until the last case (39), at which it breaks out of the switch-case statement. For all the rest, and therefore the odd-numbered cases, the "default" case catches them.

If that is what's being asked, I'm not sure why would anyone want to do this other than to illustrate switch-case fall-through. As with your first attempt, you're better off incrementing by 2.

If for some unforeseeable reason +2 increments are not possible, then it'll be better to use the modulus operator to massively simplify the switch-case statements, e.g.,

        for (int i = 20; i <= 40; i++) {
            switch (i % 2) {
                case 1:
                    break;
                default:
                    System.out.println(i);
                    break;
            }
        }

Btw, use switch-case fall-through sparingly as it can lead to bugs. It's very easy to overlook the "break" (or absence of) statement. I don't use it in my work...

Thank you for the explanation. Our instructor was using it to illustrate the switch-case fall-through, and I wanted a clearer understanding.