Java Switch

Why use switch

A switch statement evaluates one expression once and then jumps to the case label that matches its value. It works with int and other whole-number types, char, String, and enums. Compared to a stack of else if branches, a switch makes it obvious that every branch is comparing the same variable.

public class Main {
  public static void main(String[] args) {
    int day = 3;

    switch (day) {
      case 1:
        System.out.println("Monday");
        break;
      case 2:
        System.out.println("Tuesday");
        break;
      case 3:
        System.out.println("Wednesday");
        break;
      default:
        System.out.println("Another day");
    }
  }
}
// Output:
// Wednesday

The role of break and default

Each case ends with a break so that execution leaves the switch once a match is handled. Without break, Java falls through and keeps running the code in the following cases until it hits a break or the end of the switch. The optional default label runs when no case matches, acting like the else of a switch.

• case - a label to match the switch value against.
• break - stops the switch so control does not fall into the next case.
• default - the catch-all branch when nothing else matches.
• Fall-through - the behaviour where a missing break lets execution continue into the next case.

Intentional fall-through

Sometimes several values should be treated the same way. Stacking case labels with no code between them lets them share one block. Here weekdays and weekend days each map to a single message.

public class Main {
  public static void main(String[] args) {
    int day = 6;

    switch (day) {
      case 1:
      case 2:
      case 3:
      case 4:
      case 5:
        System.out.println("Weekday");
        break;
      case 6:
      case 7:
        System.out.println("Weekend");
        break;
      default:
        System.out.println("Invalid day");
    }
  }
}
// Output:
// Weekend

The modern arrow syntax

Modern Java (14 and later) offers a switch that uses arrows instead of colons. Each arrow branch runs only its own code with no fall-through, so you never need break. A switch can even be used as an expression that returns a value, which pairs nicely with the var keyword.

public class Main {
  public static void main(String[] args) {
    int day = 3;

    String name = switch (day) {
      case 1 -> "Monday";
      case 2 -> "Tuesday";
      case 3 -> "Wednesday";
      default -> "Another day";
    };

    System.out.println(name);
  }
}
// Output:
// Wednesday