Using two values for one switch case statement

Question

In my code, the program does something depending on the text entered by the user. My code looks like:

switch (name) {
        case text1: {
            //blah
            break;
        }
        case text2: {
            //blah
            break;
        }
        case text3: {
            //blah
            break;
        }
        case text4: {
            //blah
            break;
        }

However, the code inside cases text1 and text4 is the same. I was therefore wondering if it would be possible for me to implement something like

case text1||text4: {
            //blah
            break;
        }

I know that the || operator won't work in the case statement but is there something similar I can use.

Answer 1

You can use have both CASE statements as follows.

  case text1: 
  case text4:{
            //blah
            break;
        }

SEE THIS EXAMPLE:The code example calculates the number of days in a particular month:

class SwitchDemo {
    public static void main(String[] args) {

        int month = 2;
        int year = 2000;
        int numDays = 0;

        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;
        }
        System.out.println("Number of Days = "
                           + numDays);
    }
}

This is the output from the code:

Number of Days = 29

FALLTHROUGH:

Another point of interest is the break statement. Each break statement terminates the enclosing switch statement. Control flow continues with the first statement following the switch block. The break statements are necessary because without them, statements in switch blocks fall through: All statements after the matching case label are executed in sequence, regardless of the expression of subsequent case labels, until a break statement is encountered.

EXAMPLE CODE:

public class SwitchFallThrough {

    public static void main(String[] args) {
        java.util.ArrayList<String> futureMonths =
            new java.util.ArrayList<String>();

        int month = 8;

        switch (month) {
            case 1:  futureMonths.add("January");
            case 2:  futureMonths.add("February");
            case 3:  futureMonths.add("March");
            case 4:  futureMonths.add("April");
            case 5:  futureMonths.add("May");
            case 6:  futureMonths.add("June");
            case 7:  futureMonths.add("July");
            case 8:  futureMonths.add("August");
            case 9:  futureMonths.add("September");
            case 10: futureMonths.add("October");
            case 11: futureMonths.add("November");
            case 12: futureMonths.add("December");
            default: break;
        }

        if (futureMonths.isEmpty()) {
            System.out.println("Invalid month number");
        } else {
            for (String monthName : futureMonths) {
               System.out.println(monthName);
            }
        }
    }
}

This is the output from the code:

August
September
October
November
December

Using Strings in switch Statements

In Java SE 7 and later, you can use a String object in the switch statement's expression. The following code example, , displays the number of the month based on the value of the String named month:

public class StringSwitchDemo {

    public static int getMonthNumber(String month) {

        int monthNumber = 0;

        if (month == null) {
            return monthNumber;
        }

        switch (month.toLowerCase()) {
            case "january":
                monthNumber = 1;
                break;
            case "february":
                monthNumber = 2;
                break;
            case "march":
                monthNumber = 3;
                break;
            case "april":
                monthNumber = 4;
                break;
            case "may":
                monthNumber = 5;
                break;
            case "june":
                monthNumber = 6;
                break;
            case "july":
                monthNumber = 7;
                break;
            case "august":
                monthNumber = 8;
                break;
            case "september":
                monthNumber = 9;
                break;
            case "october":
                monthNumber = 10;
                break;
            case "november":
                monthNumber = 11;
                break;
            case "december":
                monthNumber = 12;
                break;
            default: 
                monthNumber = 0;
                break;
        }

        return monthNumber;
    }

    public static void main(String[] args) {

        String month = "August";

        int returnedMonthNumber =
            StringSwitchDemo.getMonthNumber(month);

        if (returnedMonthNumber == 0) {
            System.out.println("Invalid month");
        } else {
            System.out.println(returnedMonthNumber);
        }
    }
}

The output from this code is 8.

FROM Java Docs

Answer 2

You can do the following to use multiple cases for one switch statement:

case "firstCase":
case "secondCase": {
    // Run code here for both cases
}

Answer 3

The case values are just codeless "goto" points that can share the same entry point:

case text1:
case text4: 
    //blah
    break;

Note that the braces are redundant.

Answer 4

Just do

case text1: case text4: 
     do stuff;
     break;

Answer 5

With the integration of JEP 325: Switch Expressions (Preview) in JDK-12 early access builds, one can now make use of the new form of the switch label as :-

case text1, text4 -> {
     //blah
} 

or to rephrase the demo from one of the answers, something like :-

public class RephraseDemo {

    public static void main(String[] args) {
        int month = 9;
        int year = 2018;
        int numDays = 0;

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

            }
        }
        System.out.println("Number of Days = " + numDays);
    }
}

Here is how you can give it a try - Compile a JDK12 preview feature with Maven

Answer 6

The brackets are unnecessary. Just do

case text1:
case text4:
  doSomethingHere();
  break;
case text2:
  doSomethingElse()
  break;

If anyone is curious, this is called a case fallthrough. The ability to do this is the reason why break; is necessary to end case statements. For more information, see the wikipedia article http://en.wikipedia.org/wiki/Switch_statement.

Answer 7

Fall through approach is the best one i feel.

case text1:
case text4: {
        //Yada yada
        break;
} 

Answer 8

You can use:

case text1: case text4: 
     do stuff;
     break;

Answer 9

The fallthrough answers by others are good ones.

However another approach would be extract methods out of the contents of your case statements and then just call the appropriate method from each case.

In the example below, both case 'text1' and case 'text4' behave the same:

switch (name) {
        case text1: {
            method1();
            break;
        }
        case text2: {
            method2();
            break;
        }
        case text3: {
            method3();
            break;
        }
        case text4: {
            method1();
            break;
        }

I personally find this style of writing case statements more maintainable and slightly more readable, especially when the methods you call have good descriptive names.

Answer 10

The case values are just codeless "goto" points that can share the same entry point:

case text1:
case text4: {
//Do something
break;
}

Note that the braces are redundant.

Answer 11

JEP 354: Switch Expressions (Preview) in JDK-13 and JEP 361: Switch Expressions (Standard) in JDK-14 will extend the switch statement so it can be used as an expression.

Now you can:

• directly assign variable from switch expression,
• use new form of switch label (case L ->):

  The code to the right of a "case L ->" switch label is restricted to be an expression, a block, or (for convenience) a throw statement.

• use multiple constants per case, separated by commas,
• and also there are no more value breaks:

  To yield a value from a switch expression, the break with value statement is dropped in favor of a yield statement.

So the demo from one of the answers might look like this:

public class SwitchExpression {

  public static void main(String[] args) {
      int month = 9;
      int year = 2018;
      int numDays = switch (month) {
        case 1, 3, 5, 7, 8, 10, 12 -> 31;
        case 4, 6, 9, 11 -> 30;
        case 2 -> {
          if (java.time.Year.of(year).isLeap()) {
            System.out.println("Wow! It's leap year!");
            yield 29;
          } else {
            yield 28;
          }
        }
        default -> {
          System.out.println("Invalid month.");
          yield 0;
        }
      };
      System.out.println("Number of Days = " + numDays);
  }
}

Answer 12

Java 12 and above

switch (name) {
    case text1, text4 -> // do something ;
    case text2, text3, text 5 -> // do something else ;
    default -> // default case ;
}

You can also assign a value through the switch case expression :

String text = switch (name) {
    case text1, text4 -> "hello" ;
    case text2, text3, text5 -> "world" ;
    default -> "goodbye";
};

"yield" keyword

It allows you to return a value by the switch case expression

String text = switch (name) {
    case text1, text4 ->
        yield "hello";
    case text2, text3, text5 ->
        yield "world";
    default ->
        yield "goodbye";
};

Answer 13

Another variation?

  switch (name) {
    case ['text1', 'text2']:
      // do something
      break
    case 'text3':
      // do something
      break
    default:
      // do something
      break
  }