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

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    Default 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!


  2. #2
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    Default Fall-thru Switch

    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!

  3. #3
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    Default Re: Coding a statement that increments from 20-40 (only in even numbers) - fall-thru switch

    The posted code shouldn't pass any odd numbers to the switch.
    If you don't understand my answer, don't ignore it, ask a question.

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

    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...

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    Default Re: Fall-thru Switch

    nvm
    Last edited by KucerakJM; March 6th, 2014 at 12:03 PM.

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

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

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