How to convert a comparative if statement to a switch case statement?

Question

I'm new to java programming and I'm having trouble figuring this out.

Here's my code:

boolean running = true;
   PANTS:
while (running) {
    int waistMeasure = in.nextInt();

    if (waistMeasure >= 26 && waistMeasure < 28){
        System.out.println("You are a Small.");
        break;
    }
    if (waistMeasure >= 28 && waistMeasure < 30){
        System.out.println("You are a Medium.");
        break;
    }
    if (waistMeasure >= 30 && waistMeasure <= 34){
        System.out.println("You are a Large.");
        break;
    }

    else {
        System.out.println("Invalid input");
    }
}

Is there any way to convert this into switch case statements?

Actually, it's supposed to be 30 to 34. That's a mistake on my part. — Nighthawk, Jun 06 '16 at 18:39
@shmosel Medium of course. ;-) `break` prevents reaching next `if` statement. — Andreas, Jun 06 '16 at 18:39
@Nighthawk, so [fix it](http://stackoverflow.com/posts/37664519/edit). — shmosel, Jun 06 '16 at 18:39
@Alnitak it does when this code is within a for-loop, but that leaves us guessing and therefore a bad MVC example. — martijnn2008, Jun 06 '16 at 18:42
is `PANTS:` a label? You are not using a `GoTo` are you? http://www.drdobbs.com/jvm/programming-with-reason-why-is-goto-bad/228200966 — martijnn2008, Jun 06 '16 at 18:46
@martijnn2008 Yes, it's a label. No, there is no `goto` shown. Label can be used to correctly break loop if using `switch`. See [my answer](http://stackoverflow.com/a/37664706/5221149). — Andreas, Jun 06 '16 at 18:50
@martijnn2008 Java [doesn't have](http://stackoverflow.com/a/2545141/3529323) `goto`. — bcsb1001, Jun 06 '16 at 18:55

Robin Krahl · Accepted Answer · 2016-06-06T18:48:39.797

1

Yes, there is – but you’d have to create a case for each value (as shown below). You cannot express a range of values with a single case. So if you want readable and maintainable code, you should stick with ifs.

switch (waistMeasure) {
case 26:
case 27:
    System.out.println("You are a Small.");
    running = false;
    break;
case 28:
case 29:
// ....
}

edited Jun 06 '16 at 18:48

answered Jun 06 '16 at 18:44

Robin Krahl

5,268
19
32

`break` won't exit the loop anymore. – Andreas Jun 06 '16 at 18:44
@Andreas Thanks for the comment; setting `running` to `false` solves this problem. – Robin Krahl Jun 06 '16 at 18:49
I see. I was hoping there would be a way to execute a specific range of values with a single case statement, but apparently Java can't do something like that. – Nighthawk Jun 06 '16 at 18:54
@Nighthawk Correct, it cannot. – Andreas Jun 06 '16 at 19:00

shmosel · Answer 2 · 2016-06-06T18:50:59.753

0

switch (waistMeasure) {
    case 26:
    case 27:
        System.out.println("You are a Small.");
        break PANTS;
    case 28:
    case 29:
        System.out.println("You are a Medium.");
        break PANTS;
    case 30:
    case 31:
    case 32:
    case 33:
    case 34:
        System.out.println("You are a Large.");
        break PANTS;
    default
        System.out.println("Invalid input");
}

edited Jun 06 '16 at 18:50

answered Jun 06 '16 at 18:44

shmosel

49,289
6
73
138

`break` won't exit the loop anymore. Need to `break PANTS` like [my answer](http://stackoverflow.com/a/37664706/5221149). *LOL "break pants"* – Andreas Jun 06 '16 at 18:44
I guess an `if` statement isn't that bad after all... – martijnn2008 Jun 06 '16 at 18:47
@Andreas, good point. I was wondering why the label was there... – shmosel Jun 06 '16 at 18:50

score -1 · Answer 3 · answered Jun 06 '16 at 18:44

Do you mean something like this?

Notice that you have to use the PANTS label for the break statement to exit the loop, otherwise they just break from the switch and will continue looping.

PANTS: for (;;) {
    int waistMeasure = in.nextInt();
    switch (waistMeasure) {
        case 26:
        case 27:
            System.out.println("You are a Small.");
            break PANTS;
        case 28:
        case 29:
            System.out.println("You are a Medium.");
            break PANTS;
        case 30:
        case 31:
        case 32:
        case 33:
        case 34:
            System.out.println("You are a Large.");
            break PANTS;
        default:
            System.out.println("Invalid input");
    }
}

Why the downvote? Someone don't like break on label? I find it more clear than using boolean flag to control loop, especially if loop is large (cannot be seen in full on screen without scrolling). — Andreas, Jun 06 '16 at 18:56

How to convert a comparative if statement to a switch case statement?

3 Answers3