Switch-case Structure

4.2.1 Basic switch-case

The switch-case statement is a clear, readable way to run different code blocks based on the exact value of a single variable or expression.
Unlike if-else chains, which check many unrelated conditions, switch compares the same value to multiple constants.

It’s a perfect fit when you have many discrete options: days of the week, menu commands, user actions, payment status codes, HTTP response codes, or simple enums.

When a case matches the switch value, Java runs that block until it hits a break statement.
If you forget the break, the code “falls through” into the next case — which can be useful for grouping but dangerous if unintentional.

A well-written switch-case is often more readable than multiple else-if blocks and is easier to maintain.
Modern IDEs can even auto-complete switch blocks, which helps reduce errors.

Switch works with int, char, String, and enum types.
Keep your cases clean and grouped logically for maximum clarity.

Mini Lab

java
public class BasicSwitch {
    public static void main(String[] args) {
        int day = 1;

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

4.2.2 Switch with String

Modern Java (Java 7 and later) supports switch-case with String, which is a big advantage for text-based user input.
This lets you cleanly handle user commands, routes, roles, keywords, or any situation where the input is literal text.

This is especially handy in web applications: you might use it for commands from forms, API query parameters, or parsing JSON fields that represent a user action.

One thing to remember: switch-case with String is case-sensitive.
So "Admin" and "admin" are treated as different.
To avoid bugs, normalize user input using .toLowerCase() or .toUpperCase() before switching.

Also, keep your String cases short and clear.
Avoid hard-coding magic strings throughout your app — define them as constants if they are reused.

Mini Lab

java
public class SwitchString {
    public static void main(String[] args) {
        String command = "edit";

        switch (command) {
            case "view":
                System.out.println("Viewing item.");
                break;
            case "edit":
                System.out.println("Editing item.");
                break;
            case "delete":
                System.out.println("Deleting item.");
                break;
            default:
                System.out.println("Unknown command.");
                break;
        }
    }
}

4.2.3 Grouping Cases and Default

A powerful feature of switch-case is the ability to group multiple cases that should share the same result.
You simply stack case labels together without a break until the shared block.
This makes your code shorter and clearer than writing repeated blocks.

A common real-world example is grouping months into seasons or days into weekdays and weekends.

The default case handles all other values that don’t match any specific case.
This is critical for defensive programming — it prevents unexpected inputs from slipping through silently.

Always include default unless you are absolutely certain that all possible cases are covered.

Switch-grouping and default together make your logic safer, clearer, and easier to maintain, especially in input-heavy applications.

Mini Lab

java
public class SwitchGrouping {
    public static void main(String[] args) {
        int month = 7;

        switch (month) {
            case 6:
            case 7:
            case 8:
                System.out.println("It's summer!");
                break;
            case 12:
            case 1:
            case 2:
                System.out.println("It's winter!");
                break;
            default:
                System.out.println("It's another season.");
                break;
        }
    }
}