data validation with Strings

Question

I need to do some data validation to ensure that the user enters one of the 4 these 4 choices (small,medium, large, super size) I never did data validation with Strings, must be there another way for this to work?

  public static String orderSize()
{
System.out.println("What size - small, medium, large, or super size?"); 
    String sizeChoice=input.nextLine();
    while (sizeChoice != "small" + "medium" + "large" + "super"); 
    {
        System.out.println("Must be one of the sizes listed above here.");
        System.out.println("What size - small, medium, large, or super size?");
        sizeChoice=input.nextLine();

    }
    return sizeChoice;

In java, "+" with Strings denotes concatenation - so your while statement is equivalent to while (sizeChoice != "smallmediumlargesuper"). Also, get rid of the semicolon at the end of that while line - it terminates the statement - which IS the while, which means the block in the braces is not in the while loop at all ! — racraman
– racraman, Commented Dec 12, 2018 at 0:55
If there is an answer below that most suitably answers your question, then please consider to accept that answer — Scary Wombat
– Scary Wombat, Commented Dec 12, 2018 at 1:56

Ousmane D. · Accepted Answer · 2018-12-12 00:50:38Z

3

You're quite off to be honest, what I'd suggest is to first create a set holding the possible choices.

Set<String> choices = new HashSet<>(Arrays.asList("small","medium","large", "super"));

Then simply change your while loop condition to:

 while (!choices.contains(sizeChoice)){...} // while the chosen size is not in the set of choices then keep looping...

answered Dec 12, 2018 at 0:50

Ousmane D.

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1 Comment

Almir Neto Over a year ago

Good Idea. I didn't think it.

Scary Wombat · Accepted Answer · 2018-12-12 00:59:11Z

1

I would go for a simple easy to read switch statement (unlikely that this is an issue, but note that you require Java 7+ to use switch with Strings)

boolean validated = false;
while (!validated); 
{
    switch (sizeChoice) {
        case "small":
        case "medium":
        case "large":
        case "super":
            validated = true;
            break;
        default: 
            System.out.println("Must be one of the sizes listed above here.");
            System.out.println("What size - small, medium, large, or super size?");
            sizeChoice=input.nextLine();
    }
}

edited Dec 12, 2018 at 0:59

answered Dec 12, 2018 at 0:54

Scary Wombat

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Comments

Matter · Accepted Answer · 2018-12-12 00:57:13Z

0

I would do it this way:

public static int orderSize()
{
    System.out.println("What size?  \n 1. small \n 2. medium \n 3. large 4. super \n 5. cancel"); 
    int sizeChoice=input.nextInt();
    while (sizeChoice < 1 || sizeChoice > 4 ) 
    {
        System.out.println("Must be one of the sizes listed above here.");
        System.out.println("What size?  \n 1. small \n 2. medium \n 3. large 4. super \n 5. cancel");
        sizeChoice=input.nextInt();
        if(sizeChoice == 5) break;

    }
    return sizeChoice;
}

answered Dec 12, 2018 at 0:57

Matter

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Comments

Jake Holzinger · Accepted Answer · 2018-12-12 01:16:24Z

0

It looks like you want to use the Conditional-AND operator.

!"small".equals(sizeChoice) && !"medium".equals(sizeChoice) && !"large".equals(sizeChoice ) && !"super".equals(sizeChoice)

As noted by other users there is always a clever way to do the same thing. Your code also suites a do/while loop better than a while loop if you want to avoid repeating yourself.

public static String orderSize() {
    String sizeChoice = null;
    do {
        if (sizeChoice != null) {
            System.out.println("Must be one of the sizes listed.");
        }
        System.out.println("What size - small, medium, large, or super size?");
        sizeChoice = input.nextLine();
    } while (...);
    return sizeChoice;
}

edited Dec 12, 2018 at 1:16

answered Dec 12, 2018 at 0:59

Jake Holzinger

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Comments

Erik Pragt · Accepted Answer · 2018-12-12 00:56:53Z

-1

If you do validation, I assume you have a controller. If it's only 4, I'd change the input type to an Enum, and validation will work out of the box.

The following is only to illustrate what I meant, it's dummy code, and will probably not be 100% correct.

@Controller  
public class ChoiceController {

   @GetMapping("/choose")
   public void choose(SizeEnum size) {
       // rest of the owl here
   }
}

answered Dec 12, 2018 at 0:56

Erik Pragt

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