Why can't I use switch statement on a String?

Question

Is this functionality going to be put into a later Java version?

Can someone explain why I can\'t do this, as in, the technical way Java\'s switch state

Answer 1

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 the answers (1, 2) might look like this:

  public static void main(String[] args) {
    switch (args[0]) {
      case "Monday", "Tuesday", "Wednesday" ->  System.out.println("boring");
      case "Thursday" -> System.out.println("getting better");
      case "Friday", "Saturday", "Sunday" -> System.out.println("much better");
    }

Answer 2

When you use intellij also look at:

File -> Project Structure -> Project

File -> Project Structure -> Modules

When you have multiple modules make sure you set the correct language level in the module tab.

Answer 3

public class StringSwitchCase { 

    public static void main(String args[]) {

        visitIsland("Santorini"); 
        visitIsland("Crete"); 
        visitIsland("Paros"); 

    } 

    public static void visitIsland(String island) {
         switch(island) {
          case "Corfu": 
               System.out.println("User wants to visit Corfu");
               break; 
          case "Crete": 
               System.out.println("User wants to visit Crete");
               break; 
          case "Santorini": 
               System.out.println("User wants to visit Santorini");
               break; 
          case "Mykonos": 
               System.out.println("User wants to visit Mykonos");
               break; 
         default: 
               System.out.println("Unknown Island");
               break; 
         } 
    } 

} 

Answer 4

It's a breeze in Groovy; I embed the groovy jar and create a groovy utility class to do all these things and more which I find exasperating to do in Java (since I am stuck using Java 6 in the enterprise.)

it.'p'.each{
switch (it.@name.text()){
   case "choclate":
     myholder.myval=(it.text());
     break;
     }}...

Answer 5

An example of direct String usage since 1.7 may be shown as well:

public static void main(String[] args) {

    switch (args[0]) {
        case "Monday":
        case "Tuesday":
        case "Wednesday":
            System.out.println("boring");
            break;
        case "Thursday":
            System.out.println("getting better");
        case "Friday":
        case "Saturday":
        case "Sunday":
            System.out.println("much better");
            break;
    }

}

Answer 6

In Java 11+ it's possible with variables too. The only condition is it must be a constant.

For Example:

final String LEFT = "left";
final String RIGHT = "right";
final String UP = "up";
final String DOWN = "down";

String var = ...;

switch (var) {
    case LEFT:
    case RIGHT:
    case DOWN:
    default:
        return 0;
}

PS. I've not tried this with earlier jdks. So please update the answer if it's supported there too.