Java Switch Statement — Classic & Modern Switch Expressions

When you need to compare a variable against many specific values, a switch statement is cleaner than a long if-else chain.

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Classic Switch Statement

int day = 3;

switch (day) {
    case 1:
        System.out.println("Monday");
        break;
    case 2:
        System.out.println("Tuesday");
        break;
    case 3:
        System.out.println("Wednesday");
        break;
    case 4:
        System.out.println("Thursday");
        break;
    case 5:
        System.out.println("Friday");
        break;
    default:
        System.out.println("Weekend");
        break;
}
// Output: Wednesday

Rules

• The expression must be int, byte, short, char, String, or an enum.
• Each case must be a constant (literal or final variable).
• break exits the switch. Without it, execution falls through to the next case.
• default handles all unmatched values (optional but recommended).

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The Fall-Through Trap

int day = 2;

switch (day) {
    case 1:
        System.out.println("Monday");
        // no break — falls through!
    case 2:
        System.out.println("Tuesday");
        // no break — falls through!
    case 3:
        System.out.println("Wednesday");
        break;
    default:
        System.out.println("Other");
}

Output:

Tuesday
Wednesday

⚠️ Always include break unless fall-through is intentional.

Intentional Fall-Through

Sometimes useful for grouping:

switch (day) {
    case 1:
    case 2:
    case 3:
    case 4:
    case 5:
        System.out.println("Weekday");
        break;
    case 6:
    case 7:
        System.out.println("Weekend");
        break;
}

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Switch with Strings

String command = "start";

switch (command) {
    case "start":
        System.out.println("Starting...");
        break;
    case "stop":
        System.out.println("Stopping...");
        break;
    case "restart":
        System.out.println("Restarting...");
        break;
    default:
        System.out.println("Unknown command");
}

String comparison in switch is case-sensitive. Convert to lowercase first if needed: command.toLowerCase().

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Enhanced Switch Expression (Java 14+)

Modern Java offers a cleaner syntax using arrow (->):

int day = 3;

String dayName = switch (day) {
    case 1 -> "Monday";
    case 2 -> "Tuesday";
    case 3 -> "Wednesday";
    case 4 -> "Thursday";
    case 5 -> "Friday";
    case 6 -> "Saturday";
    case 7 -> "Sunday";
    default -> "Invalid";
};

System.out.println(dayName);  // Wednesday

Benefits of Arrow Syntax

• No fall-through — no need for break
• Returns a value — it’s an expression, not just a statement
• Multiple labels per case:

String type = switch (day) {
    case 1, 2, 3, 4, 5 -> "Weekday";
    case 6, 7           -> "Weekend";
    default              -> "Invalid";
};

Multi-Line Cases with yield

When a case needs more than one statement, use a block and yield:

String description = switch (day) {
    case 1 -> "Monday — Start of the week";
    case 5 -> {
        System.out.println("Almost weekend!");
        yield "Friday — TGIF!";
    }
    default -> "Regular day";
};

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Switch with Enums

Switch works beautifully with enums:

enum Season { SPRING, SUMMER, FALL, WINTER }

Season season = Season.SUMMER;

String activity = switch (season) {
    case SPRING -> "Gardening";
    case SUMMER -> "Swimming";
    case FALL   -> "Hiking";
    case WINTER -> "Skiing";
};

With enums, no default is needed if all values are covered (the compiler checks).

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Pattern Matching in Switch (Java 21+)

Java 21 introduced pattern matching for switch:

Object obj = "Hello";

String result = switch (obj) {
    case Integer i -> "Integer: " + i;
    case String s  -> "String: " + s;
    case null      -> "null";
    default        -> "Unknown: " + obj;
};

System.out.println(result);  // String: Hello

Guarded Patterns

Object obj = 42;

String result = switch (obj) {
    case Integer i when i > 0 -> "Positive integer: " + i;
    case Integer i            -> "Non-positive integer: " + i;
    case String s             -> "String: " + s;
    default                   -> "Other";
};

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When to Use Switch vs If-Else

Use Switch	Use If-Else
Comparing against specific values	Complex range conditions
Variable is int, String, or enum	Boolean expressions
Many cases to handle	2-3 simple conditions
Readability matters	Conditions involve different variables

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Quick Exercises

1. Write a switch that converts a month number (1-12) to its name.
2. Rewrite the grading example from the if-else chapter using switch expressions.
3. Write a switch that takes a char operator (+, -, *, /) and performs the calculation.

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Summary

Feature	Classic Switch	Enhanced Switch (14+)
Syntax	case X: ... break;	case X -> ...;
Fall-through	Yes (needs break)	No
Returns value	No	Yes (expression)
Multiple labels	Stacked cases	case 1, 2, 3 ->
Multi-line	Regular block	Block + yield

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What’s Next?

Decision-making is done. Now let’s learn loops — repeating actions — starting with the for loop: For Loop.