Java switch Statement

The switch statement in Java is a control flow statement used to execute one block of code from multiple options, based on the value of a single variable or expression. It is an alternative to the if-else if ladder when you are comparing a variable against multiple possible values.

Syntax:

switch (expression) {
    case value1:
        // Code to execute if expression == value1
        break;
    case value2:
        // Code to execute if expression == value2
        break;
    ...
    default:
        // Code to execute if no case matches
}

Important Points

1. Expression: The value inside the switch must be of type byte, short, int, char, String, or an enum.

2. case Values: Each case represents a potential match for the expression. The case values must be constant and unique.

3. break Statement: It prevents the execution from “falling through” to the next case. Without break, all subsequent cases are executed.

4. default Case: This is optional and executed if none of the case values match the expression.

Example: Using switch with int

public class SwitchExample {
    public static void main(String[] args) {
        int day = 2;

        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");
        }
    }
}

Output: Tuesday

Example: Using switch with String

public class SwitchWithString {
    public static void main(String[] args) {
        String color = "green";

        switch (color.toLowerCase()) {
            case "red":
                System.out.println("Stop!");
                break;
            case "yellow":
                System.out.println("Get ready.");
                break;
            case "green":
                System.out.println("Go!");
                break;
            default:
                System.out.println("Invalid color.");
        }
    }
}

Output: Go!

Example: Omitting break statement

If you omit the break statement, execution continues to the next case until a break or the end of the switch is reached.

Example:

public class SwitchFallthrough {
    public static void main(String[] args) {
        int day = 3;

        switch (day) {
            case 1:
                System.out.println("Monday");
            case 2:
                System.out.println("Tuesday");
            case 3:
                System.out.println("Wednesday");
            default:
                System.out.println("Weekend");
        }
    }
}

Output:

Wednesday
Weekend

When Default Case is executed

The default block is executed if no other case matches the expression. It is like the else in if-else.

Example:

public class ExampleSwitchDefault {
    public static void main(String[] args) {
        int number = 10;

        switch (number) {
            case 1:
                System.out.println("One");
                break;
            case 2:
                System.out.println("Two");
                break;
            default:
                System.out.println("No match found.");
        }
    }
}

Output: No match found

Using switch with enum

You can also use enum types in a switch statement.

public class SwitchWithEnum {
    enum Day { MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY }

    public static void main(String[] args) {
        Day today = Day.TUESDAY;

        switch (today) {
            case MONDAY:
                System.out.println("Start of the week!");
                break;
            case FRIDAY:
                System.out.println("Almost weekend!");
                break;
            case SATURDAY:
            case SUNDAY:
                System.out.println("It's weekend!");
                break;
            default:
                System.out.println("It's a weekday.");
        }
    }
}

Output: It’s a weekday.

Limitations of switch

1. switch cannot handle range-based conditions (<, >, etc.).

Example: switch cannot check if (age > 21) or if (age < 21).

2. It works only with primitive types (byte, short, int, char), String, or enum.