Java 12 - Switch Expressions


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Java 12 introduces expressions to Switch statement and released it as a preview feature. Following are the changes introduced in case of new switch with expressions −

  • No fallthrough.
  • No break statment required to prevent fallthrough.
  • A single case can have multiple constant labels.
  • Default case is compulsary now.

Consider the following example −

ApiTester.java

public class APITester {

   public static void main(String[] args) {
      System.out.println("Old Switch");
      System.out.println(getDayTypeOldStyle("Monday"));
      System.out.println(getDayTypeOldStyle("Saturday"));
      System.out.println(getDayTypeOldStyle(""));

      System.out.println("New Switch");
      System.out.println(getDayType("Monday"));
      System.out.println(getDayType("Saturday"));
      System.out.println(getDayType(""));
   }

   public static String getDayType(String day) {

      String result = switch (day) {
         case "Monday", "Tuesday", "Wednesday","Thursday", "Friday" -> "Weekday";
         case "Saturday", "Sunday" -> "Weekend";
         default -> {
            break "Invalid day.";            
         }
      };
      return result;
   }

   public static String getDayTypeOldStyle(String day) {
      String result = null;

      switch (day) {
         case "Monday":
         case "Tuesday":
         case "Wednesday":
         case "Thursday":
         case "Friday":
            result = "Weekday";
            break;
         case "Saturday": 
         case "Sunday":
            result = "Weekend";
            break;
         default:
            result =  "Invalid day.";            
      }

      return result;
   }
}

Compile and Run the program

$javac -Xlint:preview --enable-preview -source 12 APITester.java

$java --enable-preview APITester

Output

Old Switch
Weekday
Weekend
Invalid day.
New Switch
Weekday
Weekend
Invalid day.
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