switch with enum

Learn to use enums with switch.

Use enums with switch

switch is ideal for branching on an enum constant. Each case writes the constant name directly; no Day. prefix is added.

Day d = Day.FRIDAY;
switch (d) {
  case MONDAY: System.out.println("Hafta başı"); break;
  case FRIDAY: System.out.println("Hafta sonu yakın"); break;
}

The constant name appears bare after case; writing case Day.MONDAY: is a compile error. Without break, branches fall through. The default branch catches all remaining constants.

The default branch

The default branch runs when no case matches. If the switch covers all constants, default is unnecessary; but it is a safety net when new constants are added.

switch (d) {
  case SATURDAY:
  case SUNDAY: System.out.println("Hafta sonu"); break;
  default: System.out.println("Hafta içi");
}

To bind multiple constants to the same branch, write case labels back to back. default is placed last but its position is flexible. When a new constant is added, the compiler can warn if the switch is no longer exhaustive.

Exercise Print a message for a day

Define the Day enum (at least MONDAY and FRIDAY). Build a switch for Day.FRIDAY; in the case FRIDAY branch print Hafta sonu yakın. Start with Day d = Day.FRIDAY;.

Show example solution

enum Day { MONDAY, FRIDAY }
// inside main:
Day d = Day.FRIDAY;
switch (d) {
  case FRIDAY: System.out.println("Hafta sonu yakın"); break;
}

Test yourself

What do you write after case when using switch with an enum?
- "MONDAY"
- MONDAY
- Day.MONDAY
- Day
Show answer

MONDAY — the constant name is written bare after case; no Day. prefix.

Complete the case branch

switch (d) {
  case MONDAY: System.out.println("Hafta başı"); ____
  case FRIDAY: System.out.println("Hafta sonu yakın"); break;
}

Show answer

switch (d) {
  case MONDAY: System.out.println("Hafta başı"); break
  case FRIDAY: System.out.println("Hafta sonu yakın"); break;
}

Match each constant to its output

MONDAY

Start of week
FRIDAY

Weekend near
SUNDAY

Weekend
WEDNESDAY

Middle day

Next lesson: Summary - Enum

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