Today, we’re diving into another fundamental concept in Java programming: the switch statement. If you’ve already learned about the if statement (if not, check out this article about if), you’ll find that switch is another way to make decisions in your code. In some cases, it can make your programs more readable and efficient.

When to Use if vs. switch?

Here’s a simple guideline:

• Use if when:
  • You need to check a few different conditions, especially if they involve ranges or logical operators (e.g., age > 18 && age < 65).
  • Conditions are varied, like checking numbers, strings, or complex expressions.
• Use switch when:
  • You’re checking a single variable against several possible values.
  • You want cleaner and more readable code compared to a long chain of if-else statements.

What Does switch Look Like?

Here’s the basic structure of a switch statement:

switch (variable) {
    case value1:
        // Actions to perform if variable == value1
        break;
    case value2:
        // Actions to perform if variable == value2
        break;
    default:
        // Actions to perform if none of the cases match
}

Key points:

1. variable is the value being tested.
2. Each case checks if the variable matches a specific value.
3. The break statement prevents the code from “falling through” to the next case.
4. The default block runs if no cases match (like else in an if statement).

Example 1: Checking the Day of the Week

Let’s write a program that tells us what day it is based on a number (1 = Monday, 2 = Tuesday, etc.).

public class WeekDay {
    public static void main(String[] args) {
        int day = 3; // Day of the week

        switch (day) {
            case 1:
                System.out.println("It's Monday.");
                break;
            case 2:
                System.out.println("It's Tuesday.");
                break;
            case 3:
                System.out.println("It's Wednesday.");
                break;
            case 4:
                System.out.println("It's Thursday.");
                break;
            case 5:
                System.out.println("It's Friday.");
                break;
            case 6:
                System.out.println("It's Saturday.");
                break;
            case 7:
                System.out.println("It's Sunday.");
                break;
            default:
                System.out.println("Invalid day number!");
        }
    }
}

Explanation:

• If day = 3, the program prints: “It’s Wednesday.”
• If day = 8, it falls to the default block: “Invalid day number!”

Example 2: Grading System

Imagine a school where grades are represented by letters (A, B, C, D, F). Let’s use switch to display feedback based on the grade.

public class GradeCheck {
    public static void main(String[] args) {
        char grade = 'B'; // Student's grade

        switch (grade) {
            case 'A':
                System.out.println("Excellent!");
                break;
            case 'B':
                System.out.println("Good job!");
                break;
            case 'C':
                System.out.println("Satisfactory.");
                break;
            case 'D':
                System.out.println("Needs improvement.");
                break;
            case 'F':
                System.out.println("Fail.");
                break;
            default:
                System.out.println("Unknown grade.");
        }
    }
}

Why Use switch?

Let’s compare a switch with a similar if-else chain:

if (grade == 'A') {
    System.out.println("Excellent!");
} else if (grade == 'B') {
    System.out.println("Good job!");
} else if (grade == 'C') {
    System.out.println("Satisfactory.");
} else if (grade == 'D') {
    System.out.println("Needs improvement.");
} else if (grade == 'F') {
    System.out.println("Fail.");
} else {
    System.out.println("Unknown grade.");
}

As you can see, the switch version is cleaner and easier to read, especially when there are many conditions to check.

Example 3: Handling Multiple Cases Together

Sometimes, multiple cases should trigger the same action. For example, let’s check if today is a weekend:

public class Weekend {
    public static void main(String[] args) {
        int day = 6; // Day of the week

        switch (day) {
            case 6: // Saturday
            case 7: // Sunday
                System.out.println("It's the weekend! Time to relax.");
                break;
            default:
                System.out.println("It's a weekday. Back to work!");
        }
    }
}

What to Keep in Mind About switch

1. switch is great for simple equality checks – when you’re comparing one variable to multiple values.
2. It keeps your code clean – especially when compared to long chains of if-else statements.
3. Don’t forget the break statement – it stops the code from executing the next cases unintentionally.
4. The default block is optional – but it’s a good habit to include it for handling unexpected values.

Practice Challenges

Here are some fun challenges to practice your switch skills:

1. Check the month by number: Write a program that prints the name of a month (1 = January, 2 = February, etc.).
2. Animal guessing game: Write a program that assigns animals to numbers (1 = Dog, 2 = Cat, 3 = Lion) and prints the result.
3. Extended grading system: Modify the grade example to include A+ and A- for more detailed feedback.

The switch statement is a powerful tool for simplifying your code when you need to compare one value against multiple options. It’s a great complement to the if statement, and now you know when to use each. Happy coding!