Switches in Java: Can I include a condition in a case? [duplicate]

Question

Here is my code:

switch(age) {
    case 10:
        System.out.println("You are too young to drive.");
        break;
    case 20:
        System.out.println("You can drive!");
        break;
    default:
        System.out.println("Error");
}

What happens if the age is 15? Well, it gives me an error. So I was wondering if it's possible to include a condition within the case. For example,

case (age>=10 && age<=20):
   System.out.println("You're still too young to drive...");
   break;

I could use an if statement, but I'm wondering if this is possible with a switch.

Answer 1

case Requires a Constant Expression

No. It's not possible because a case must be a constant expression. But you could (as you guessed) use an if. Logically, anyone under 20 (assuming that's the legal age) is too young to drive.

final int drivingAge = 20;
if (age < drivingAge) {
    System.out.printf("%d is too young to drive...%n", age);
} else {
    System.out.printf("%d is old enough to drive.%n", age);
}

Alternatively

That could be written with ? : conditional operator (aka a ternary expression; note some people find the ternary difficult to read) like

final int drivingAge = 20;
System.out.printf(age < drivingAge ? "%d is too young to drive...%n"
        : "%d is old enough to drive.%n", age);

Answer 2

Because of fall-through you can do this:

switch(age){
    case 10:  
    case 11:
    case 12:
    case 13:
    case 14:
    case 15:
    case 16:
    case 17:
    case 18:
    case 19:
        System.out.println("You are too young to drive.");
        break;  
    case 20:
        System.out.println("You can drive!");
        break;
    default:
        System.out.println("Error");
}

It is a little more code but it accomplishes the same thing.

Answer 3

No, in Java you cannot do it. Use if statement instead. Constructs similar to what you want exist in other languages like Scala.

Answer 4

You can't do this in Java. A switch jumps to the case that matches the value you're switching on. You can't use expressions of age inside the case. However, you can use something called a "fallthrough" (see here and search for "fall through").

So, for your example, you could do something like:

switch(age)
{
    case 10:
    case 11:
    case 12:
    case 13:
    case 14:
    case 15:
    case 16:
    case 17:
    case 18:
    case 19:
        System.out.println("You are too young to drive.");
        break;

    case 20:
    case 21:
        System.out.println("You can drive!");
        break;

    default:
        System.out.println("Error");
 }

However, your problem is best solved with an if.

Answer 5

Sadly, it's not possible in Java. You'll have to resort to using if-else statements.You can try this, which is very repetitive.

  switch(age){ 
    case 10: case 11: case 12: case 13: case 14: case 15:
    //And So on
    System.out.println("You are too young to drive.");
        break;
    case 20:
        System.out.println("You can drive!");
        break;
    default:
        System.out.println("Error");
    }

Try if statement

   public void canDrive(int age){

   if(age <= 19){
       System.out.println("You are too young to drive.")
   }
   else{
       System.out.println("You can drive!");}
   }