Reputation: 3673

Using switch statement with a range of value in each case?

In Java, is it possible to write a switch statement where each case contains more than one value? For example (though clearly the following code won't work):

switch (num) {
    case 1 .. 5:
        System.out.println("testing case 1 to 5");
        break;
    case 6 .. 10:
        System.out.println("testing case 6 to 10");
        break;
}

I think this can be done in Objective C, are there a similar thing in Java? Or should I just use if, else if statements instead?

Upvotes: 115

Answers (21)

cuh

Reputation: 3800

With Java 20 (JEP 433 Pattern Matching for switch (Fourth Preview)) this feature is available.

Integer integer = ...;
switch (integer) {
    case Integer i when i > 0 && i <= 5 -> System.out.println("testing case 1 to 5");
    case Integer i when i > 5 && i <= 10 -> System.out.println("testing case 6 to 10");
    default -> System.out.println("All the remaining integers");
}

Upvotes: 0

A_Arnold

Reputation: 4039

Java 12+

It is supported as of Java 12. Check out JEP 354. No "range" possibilities here, but can be useful either.

switch (day) {
    case MONDAY, FRIDAY, SUNDAY -> System.out.println(6);//number of letters
    case TUESDAY                -> System.out.println(7);
    case THURSDAY, SATURDAY     -> System.out.println(8);
    case WEDNESDAY              -> System.out.println(9);
}

You should be able to implement that on ints too. Note through that your switch statement have to be exhaustive (using default keyword, or using all possible values in case statements).

Java 20+

UPDATE: As of Java 20 (March '23) this is possible! Check out JEP 433. Their example is if you want to test for a triangle of a certain size.

switch (s) {
        case null -> 
            { break; }
        case Triangle t
        when t.calculateArea() > 100 ->
            System.out.println("Large triangle");
        default ->
            System.out.println("A shape, possibly a small triangle");
    }

Upvotes: 15

Prectron

Reputation: 495

Apart from switch statements, since Java 14 SE there are switch expressions you can use as an alternative when each case produces some result. If handling a non-integer Math.round() can be used, for example.

String result = switch (Math.round(value)) {
    case 1, 2, 3, 4, 5:
        // handle case 1
        yield "result of case 1";
    case 6, 7, 8, 9, 10:
        // handle case 2
        yield "result of case 2";
    default:
        // handle the default case
        yield "result of the default case";
}

System.out.println("result = " + result);

The difference from the switch statement is that all cases must be covered (often with the default case).

Upvotes: 1

ClassY

Reputation: 655

after reading all the comments I didn't see anybody mention enhanced switch in which you can have multiple values in one case like this ->

switch(value){
   case 1,2,3,4:
      //dosth
      break;
   case 7,9,10,23:
      //dosth
      break;
}

and since in your case, there is only one expression in every case, you can do the following without the need to break every case->

switch (value) {
    case 1, 2, 3, 4 -> System.out.println("one of 1,2,3,4 matched");
    case 7, 9, 10, 23 -> System.out.println("one of 7,9,10,23 matched");
}

this is one of the many added benefits with enhanced switches in java.

Upvotes: 8

wicas

Reputation: 1

Excellent contributions. In case it may be still helpful, I found an option to analyze whether inside a string there are characters different from letters and spaces:

string name = scEntry.nextLine();
int len = name.length(); 
int s = 0;
do { 
     int asc = name.codePointAt(s);
     switch ((asc == 32) ? 0 : (64 < asc && asc < 91) ? 1 : 
             (96 < asc && asc < 123) ? 2 : 99) {
         case 0, 1, 2 -> {
                  s++; 
                  break;
         }
         case 99 -> {
           s = 0;
           System.out.println("Type in only letters [A-Za-z]
                             or spaces");
           System.out.print("Type the user name again: ");
           name = scEntry.nextLine();
           len = name.length();
           break;
         }
} while (s < len);
s = 0;

In this example, the letters' ASCII codes along with the "space" ASCII code are grouped and represented by the numbers 0, 1 or 2. ASCII codes different from the above mentioned, are grouped in the value "99", so I can inform any thing about them to the user.

Upvotes: 0

Williem

Reputation: 1137

Here is a beautiful and minimalist way to go

(num > 1 && num < 5) ? first_case_method() 
                     : System.out.println("testing case 1 to 5")
                     : (num > 5 && num < 7)  ? System.out.println("testing case 5 to 7") 
                     : (num > 7 && num < 8)  ? System.out.println("testing case 7 to 8") 
                     : (num > 8 && num < 9)  ? System.out.println("testing case 8 to 9") 
                     : ... 
                     : System.out.println("default");

Upvotes: 3

isoplayer

Reputation: 103

This type of behavior is not supported in Java. However, if you have a large project that needs this, consider blending in Groovy code in your project. Groovy code is compiled into byte code and can be run with JVM. The company I work for uses Groovy to write service classes and Java to write everything else.

Upvotes: 0

zemiak

Reputation: 401

For input number in range 0..100

int n1 = 75; // input value
String res; int n=0; 
int[] a ={0,20,35,55,70,85,101};

for(; n1>=a[n]; n++);
switch(6-n+1) {
  case 1: res="A"; break;
  case 2: res="B"; break;
  case 3: res="C"; break;
  case 4: res="D"; break;
  case 5: res="E"; break;
  default:res="F";
}
System.out.println(res);

Upvotes: 1

Jitendra

Reputation: 129

  case 1: case 2: case 3: case 4: case 5: 
         System.out.println("testing case 1 to 5");
         break;
  case 6: case 7: case 8: case 9: case 10:
         System.out.println("testing case 6 to 10");
         break;
  default:
         System.out.println("default");

Upvotes: 12

DarkHark

Reputation: 693

I know this post is old but I believe this answer deserves some recognition. There is no need to avoid the switch statement. This can be done in java but through the switch statement, not the cases. It involves using ternary operators.

public class Solution {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int num = Integer.parseInt(sc.nextLine());

        switch ((1 <= num && num <= 5 ) ? 0 :
                (6 <= num && num <= 10) ? 1 : 2) {

            case 0:
                System.out.println("I'm between one and five inclusive.");
                break;
            case 1:
                System.out.println("I'm between 6 and 10 inclusive.");
                break;
            case 2:
                System.out.println("I'm not between one and five or 6 and 10 inclusive.");
                break;
        }
    }
}

Upvotes: 24

missingfaktor

Reputation: 92056

Java has nothing of that sort. Why not just do the following?

public static boolean isBetween(int x, int lower, int upper) {
  return lower <= x && x <= upper;
}

if (isBetween(num, 1, 5)) {
  System.out.println("testing case 1 to 5");
} else if (isBetween(num, 6, 10)) {
  System.out.println("testing case 6 to 10");
}

Upvotes: 117

erickson

Reputation: 269787

Use a NavigableMap implementation, like TreeMap.

/* Setup */
NavigableMap<Integer, Optional<String>> messages = new TreeMap<>();
messages.put(Integer.MIN_VALUE, Optional.empty());
messages.put(1, Optional.of("testing case 1 to 5"));
messages.put(6, Optional.of("testing case 6 to 10"));
messages.put(11, Optional.empty());

/* Use */
messages.floorEntry(3).getValue().ifPresent(System.out::println);

Upvotes: 5

Oyzuu

Reputation: 371

Or you could use your solo cases as intended and use your default case to specify range instructions as :

switch(n) {
    case 1 : System.out.println("case 1"); break;
    case 4 : System.out.println("case 4"); break;
    case 99 : System.out.println("case 99"); break;
    default :
        if (n >= 10 && n <= 15)
            System.out.println("10-15 range"); 
        else if (n >= 100 && n <= 200)
            System.out.println("100-200 range");
        else
            System.out.println("Your default case");
        break;   
}

Upvotes: 6

unnamed eng

Reputation: 328

Try this if you must use switch.

public static int range(int num){ 
    if ( 10 < num && num < 20)
        return 1;
    if ( 20 <= num && num < 30)
        return 2;
    return 3;
}

public static final int TEN_TWENTY = 1;
public static final int TWENTY_THIRTY = 2;

public static void main(String[]args){
    int a = 110;
    switch (range(a)){
        case TEN_TWENTY: 
            System.out.println("10-20"); 
            break;
        case TWENTY_THIRTY: 
            System.out.println("20-30"); 
            break;
        default: break;
    }
}

Upvotes: 6

Alexander Malakhov

Reputation: 3529

@missingfaktor 's answer is indeed correct but a bit over-complicated. Code is more verbose (at least for continuous intervals) then it could be, and requires overloads/casts and/or parameterization for long, float, Integer etc

if (num < 1)
    System.Out.Println("invalid case: " + num); // you should verify that anyway
else if (num <= 5)
    System.Out.Println("1 to 5");
else if (num <= 10)
    System.Out.Println("6 to 10");
else if (num <= 42)
    System.Out.Println("11 to 42");
else    
    System.Out.Println("43 to +infinity");

Upvotes: 2

Elliott Frisch

Reputation: 201477

You could use an enum to represent your ranges,

public static enum IntRange {
  ONE_TO_FIVE, SIX_TO_TEN;
  public boolean isInRange(int v) {
    switch (this) {
    case ONE_TO_FIVE:
      return (v >= 1 && v <= 5);
    case SIX_TO_TEN:
      return (v >= 6 && v <= 10);
    }
    return false;
  }

  public static IntRange getValue(int v) {
    if (v >= 1 && v <= 5) {
      return ONE_TO_FIVE;
    } else if (v >= 6 && v <= 10) {
      return SIX_TO_TEN;
    }
    return null;
  }
}

Upvotes: 4

Hayi Nukman

Reputation: 1201

other alternative is using math operation by dividing it, for example:

switch ((int) num/10) {
    case 1:
        System.out.println("10-19");
        break;
    case 2:
        System.out.println("20-29");
        break;
    case 3:
        System.out.println("30-39");
        break;
    case 4:
        System.out.println("40-49");
        break;
    default:
        break;
}

But, as you can see this can only be used when the range is fixed in each case.

Upvotes: 36

FSP

Reputation: 4827

No you can't do that. The best you can do is that

case 1:
case 2:
case 3:
case 4:
case 5: 
  System.Out.Println("testing case 1 to 5");
break;

Upvotes: 4

Óscar López

Reputation: 236064

It's possible to group several conditions in the same case statement using the mechanism of fall through allowed by switch statements, it's mentioned in the Java tutorial and fully specified in section §14.11. The switch Statement of the Java Language Specification.

The following snippet of code was taken from an example in the tutorial, it calculates the number of days in each month (numbered from month 1 to month 12):

switch (month) {
    case 1: case 3: case 5:
    case 7: case 8: case 10:
    case 12:
        numDays = 31;
        break;
    case 4: case 6:
    case 9: case 11:
        numDays = 30;
        break;
    case 2:
        if (((year % 4 == 0) && 
             !(year % 100 == 0))
             || (year % 400 == 0))
            numDays = 29;
        else
            numDays = 28;
        break;
    default:
        System.out.println("Invalid month.");
        break;
}

As you can see, for covering a range of values in a single case statement the only alternative is to list each of the possible values individually, one after the other. As an additional example, here's how to implement the pseudocode in the question:

switch(num) {
    case 1: case 2: case 3: case 4: case 5:
        System.out.println("testing case 1 to 5");
        break;
    case 6: case 7: case 8: case 9: case 10:
        System.out.println("testing case 6 to 10");
        break;
}

Upvotes: 4

user798182

Reputation:

I don't think you can do that in Java. Best bet is to just put the code in the last case of the range.

switch (num) {
  case 1: case 2: case 3: case 4: case 5: 
     System.Out.Println("testing case 1 to 5");
     break;
  case 6: case 7: case 8: case 9: case 10:
     System.Out.Println("testing case 6 to 10");
     break;
  default:
     //
}

Upvotes: 15

Jeffrey

Reputation: 44808

The closest you can get to that kind of behavior with switch statements is

switch (num) {
case 1:
case 2:
case 3:
case 4:
case 5:
     System.out.println("1 through 5");
     break;
case 6:
case 7:
case 8:
case 9:
case 10:
     System.out.println("6 through 10");
     break;
}

Use if statements.

Upvotes: 83

Using switch statement with a range of value in each case?

Answers (21)

Java 12+

Java 20+

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