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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.

Practice 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;.

Starter code

Main.java
public class Main {
  public static void main(String[] args) {
    // Define the Day enum, assign FRIDAY to d, print a message with switch
  }
}

// Define the Day enum here

Sample solution

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

Expected output

Hafta sonu yakın

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What do you write after case when using switch with an enum?

  • "MONDAY"
  • MONDAY Correct answer
  • Day.MONDAY
  • Day

Explanation: the constant name is written bare after case; no Day. prefix.

2 Complete the case branch

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

Explanation: break exits the branch; without it, branches fall through.

3 Match each constant to its output

Term Meaning
MONDAY Start of week
FRIDAY Weekend near
SUNDAY Weekend
WEDNESDAY Middle day

All lessons in Beginner

1 Java basics

  1. What is Java?
  2. The main method
  3. Comments
  4. Class skeleton
  5. javac and java
  6. Summary - Java basics

2 Variables

  1. int and double
  2. boolean
  3. String
  4. Naming variables
  5. final variables
  6. Summary - Variables

3 Data types

  1. Primitive types
  2. Type casting
  3. String concatenation
  4. Math class
  5. BigInteger and BigDecimal
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add/subtract
  3. Multiply/divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic
  2. Comparison
  3. Logical
  4. Bitwise
  5. Assignment and increment
  6. Summary - Operators

6 String basics

  1. length and charAt
  2. equals and equalsIgnoreCase
  3. indexOf and substring
  4. toUpperCase and trim
  5. String.format
  6. Summary - String basics

7 Conditionals

  1. The if statement
  2. else and else if
  3. Nested if
  4. switch
  5. Ternary
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. do-while
  4. break and continue
  5. for-each
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Updating quantity
  5. Putting it together

10 Arrays

  1. Declaring arrays
  2. Array access
  3. Filling arrays
  4. Multi-dimensional arrays
  5. Copying arrays
  6. Summary - Arrays

11 Array methods

  1. Arrays.sort
  2. Arrays.toString
  3. Arrays.binarySearch
  4. Arrays.copyOf
  5. Arrays.fill
  6. Summary - Array methods

12 Collections

  1. ArrayList
  2. add and get
  3. HashMap
  4. put and get
  5. HashSet
  6. Summary - Collections

13 Methods

  1. Defining methods
  2. return
  3. void methods
  4. Method overloading
  5. Scope
  6. Summary - Methods

14 Method parameters

  1. Primitive parameters
  2. Object parameters
  3. varargs
  4. Multiple values via array
  5. final parameters
  6. Summary - Method parameters

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 String builder

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  2. append
  3. insert and delete
  4. reverse
  5. toString
  6. Summary - String builder

17 Input and output

  1. Scanner
  2. nextInt and nextLine
  3. System.out.printf
  4. BufferedReader
  5. try-with-resources
  6. Summary - Input and output

18 Enum

  1. Declaring enums
  2. values and valueOf
  3. Enum fields
  4. Enum methods
  5. switch with enum
  6. Summary - Enum

19 Exception basics

  1. try/catch
  2. finally
  3. throw
  4. Exception hierarchy
  5. Multiple catch
  6. Summary - Exception basics

20 Beginner final

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  2. Data model
  3. Business logic
  4. Error handling
  5. Putting it together