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Summary - Enum

Combine values, methods and switch to write a seasons app.

Summary - Enum

In this group you learned to declare enums, work with values and valueOf, add fields and methods, and branch with switch. Enums are a safe and readable way to handle fixed sets of constants.

Now you will combine everything to write a small seasons app: define a Season enum and produce a label and a message for each constant. This summary lesson has 5 steps and includes one code task.

Practice Seasons app

Define a Season enum with SPRING and SUMMER constants. Each constant takes a String label (SPRING gets ilkbahar, SUMMER gets yaz). Start with Season s = Season.SPRING;, use switch to print ilkbahar in the SPRING branch.

Starter code

Main.java
public class Main {
  public static void main(String[] args) {
    // Define the Season enum, assign SPRING, print the label with switch
  }
}

// Define the Season enum here

Sample solution

Main.java
enum Season {
  SPRING("ilkbahar"), SUMMER("yaz");
  String label;
  Season(String label) { this.label = label; }
}
// inside main:
Season s = Season.SPRING;
switch (s) {
  case SPRING: System.out.println(s.label); break;
}

Expected output

ilkbahar

Questions and answers

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

1 Match each concept to its purpose

Term Meaning
values() All constants
valueOf() Constant from name
switch Branching
ordinal() Order number

2 Find a constant with valueOf

Question 
Season s = Season.____("SUMMER");
Answer 
Season s = Season.valueOf("SUMMER");

Explanation: valueOf produces a constant from a name.

3 What is the advantage of using an enum over using strings?

  • Typos are caught at compile time Correct answer
  • Less code is written
  • It runs faster
  • It uses less memory

Explanation: enum constants are checked at compile time; a wrong name is a compile error.

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

  1. StringBuilder
  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

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