java switch statement many cases simplified

Question

So lets say a switch statment is,

switch (month) {  
    case 1: monthString = "January";  
        break;  
    case 2: monthString = "February";  
        break;  
    case 3: monthString = "March";  
        break;  
    case 4: monthString = "April";  
        break;  
    case 5: monthString = "May";  
        break;

Is it possible to shorten that to something like

switch (month) {
    cases 1-3: monthString = "January";
        break;
    case 4-5: monthString = "April";
        break;

So that multiple case numbers are under one case? I'm doing it as I have 100 cases. 30 lead to one answer, 20 to another, 5 to another etc... so if I can use multiple cases I should cut down the bulk of the code by alot. I should also mention at each case I will want to do a few things and if I use a series of if else statements it only lets me perform one action so I cannot seem to go that route. Thanks for any help! sorry I'm new at this!

You can use case statements like -- case 1: case 2: case 3: -- etc... — Nikhil Joshi, Jul 25 '14 at 03:52

Braj · Accepted Answer · 2014-07-25T04:10:12.247

4

Is it possible to shorten that to something like

It's better explained in Java Tutorial The switch Statement

Yes you can do it.

Some of the key points:

Don't forget to add the break statement.
Add single break statement after all grouped cases.
Never forget to add default case as well.

sample code:

    int month = 1;
    String monthString = null;

    switch (month) {
        case 1:
        case 2:
        case 3:
            monthString = "January";
            break;
        case 4:
        case 5:
            monthString = "April";
            break;
        ...
        default:
            ...
    }

edited Jul 25 '14 at 04:10

answered Jul 25 '14 at 03:45

Braj

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When doing something like this you should leave a comment in the code that this was intended. – Charles Smartt Aug 15 '14 at 03:34
What do you mean? Does intend change the logic of the program? – Braj Aug 15 '14 at 04:30
As part of my job I maintain code. There is no documentation, all I can do is read and run it. If you use fall through cases, there are two reasons - it is intentional or it was a mistake. I ran into such a problem. It is just a comment, like //intentional – Charles Smartt Aug 15 '14 at 12:46

score 2 · Answer 2 · answered Jul 25 '14 at 03:57

2

You might consider an array.

static String[] MONTHS = ",January,January,January,April,April".split(",");

monthString = MONTHS[month];

answered Jul 25 '14 at 03:57

Peter Lawrey

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score 1 · Answer 3 · answered Jul 25 '14 at 04:11

I'm doing it as I have 100 cases. 30 lead to one answer, 20 to another, 5 to another etc

based on that why not compare size of the int instead of using a lot of fall-through cases. No matter what you do 100 cases, will still be a lot of tedious code to write but i can't imagine any one doing 30 fall through cases or 20 fall through case. Since your comparing int not String you can go with if statements like so:

 if (month > 0 && month <= 30) {
    monthString = "January";
 }

 else if (month > 30 && month <= 50) {
    monthString = "February";
 }

 else if (month > 50 && month <= 55) {
    monthString = "March";
 }

 // 55 cases have been matched

compared to:

switch (month) {
    case 1:
    case 2:
    case 3:
    ...
    case 28:
    case 29:
    case 30:
        monthString = "January";
        break;
}

score 0 · Answer 4 · answered Jul 25 '14 at 03:46

If I understand your question then yes. But it's not

switch (month) {
cases 1-3: monthString = "January";
    break;
case 4-5: monthString = "April";
    break;
}

It would be

switch (month) {
cases 1: case 2: case 3: monthString = "January";
    break;
case 4: case 5: monthString = "April";
    break;
}

Case statements fall through without a break. Also, you may want a default: it's like an else if your number might be outside any explicit case.

score 0 · Answer 5 · answered Jul 25 '14 at 03:46

0

yes it is possible

switch (month) {  
    case 1: 

    case 2:   

    case 3:  monthString = "January";   
        break;  
    case 4: 

    case 5:  
        monthString = "April";

answered Jul 25 '14 at 03:46

SpringLearner

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score 0 · Answer 6 · answered Jul 25 '14 at 03:55

0

Just use an if-else. It will be easier for this scenario.

answered Jul 25 '14 at 03:55

Charles Smartt

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Nice alternative, I agree with Charles. – Nikhil Joshi Jul 25 '14 at 03:56

score 0 · Answer 7 · edited May 23 '17 at 11:57

You could use a hashmap:

HashMap mySet = new HashMap()

and then fill it with the appropriate sets:

(new Integer(1), "January")

(new Integer(2), "January")

(new Integer(3), "January")

(new Integer(4), "April")

(new Integer(5), "April")

then your code looks like:

monthString = null;
mySet.containsKey(new Integer(month)) && monthString = mySet.getValue(new Integer(month))

That way you're taking advantage of short circuiting and having

"monthString = mySet.getValue(new Integer(month))"

only execute if that key is in the set. You can also make a function which populates your HashMap, thereby making it easy to maintain.

You can read up more on short-circuiting in java here: Java logical operator short-circuiting

score 0 · Answer 8 · answered Jul 25 '14 at 04:08

0

switch (month) {

  case 1:
  case 2:
  case 3:
  monthString = "January";
    break;
  case 4:
  case 5:
  monthString = "April";
    break;
}

You can use this and split function given by @Peter works great.

answered Jul 25 '14 at 04:08

Deepanshu J bedi

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java switch statement many cases simplified

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