switch Keyword in Java

The switch keyword in Java is used to execute one block of code among many alternatives. It is a control statement that allows the variable to be tested for equality against a list of values, each with its own block of code.

Usage

The switch statement provides a cleaner and more readable way to handle multiple conditional branches compared to using multiple if-else statements.

Syntax

switch (expression) {
    case value1:
        // code block
        break;
    case value2:
        // code block
        break;
    // more cases...
    default:
        // default code block
}

• expression: The variable or expression whose value is compared against the case values.
• case value: A constant value that the expression is compared to. If they match, the corresponding code block is executed.
• break: Terminates the switch statement, preventing fall-through.
• default: Executes if no case value matches the expression.

Examples

Example 1: Basic Usage

public class SwitchExample {
    public static void main(String[] args) {
        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;
            case 6:
                System.out.println("Saturday");
                break;
            case 7:
                System.out.println("Sunday");
                break;
            default:
                System.out.println("Invalid day");
        }
    }
}

In this example, the variable day is compared against the case values. Since day is 3, the output will be "Wednesday".

Example 2: Using Strings

public class SwitchStringExample {
    public static void main(String[] args) {
        String fruit = "Apple";
        switch (fruit) {
            case "Apple":
                System.out.println("Fruit is Apple");
                break;
            case "Banana":
                System.out.println("Fruit is Banana");
                break;
            case "Cherry":
                System.out.println("Fruit is Cherry");
                break;
            default:
                System.out.println("Unknown fruit");
        }
    }
}

This example demonstrates how to use a switch statement with String values. Since fruit is "Apple", the output will be "Fruit is Apple".

Example 3: Fall-Through Behavior

public class SwitchFallThroughExample {
    public static void main(String[] args) {
        int num = 2;
        switch (num) {
            case 1:
                System.out.println("One");
            case 2:
                System.out.println("Two");
            case 3:
                System.out.println("Three");
                break;
            default:
                System.out.println("Default case");
        }
    }
}

In this example, the absence of break statements results in fall-through behavior. Since num is 2, the output will be:

Two
Three
Default case

Tips and Best Practices

• Use break Statements: Always use break statements to prevent fall-through unless explicitly desired.
• Default Case: Include a default case to handle unexpected values.
• Constant Values: Ensure that case values are constants or literals.
• Type Compatibility: The switch expression can be of types byte, short, char, int, String, or an enum type. Ensure the case values are compatible with the type of the expression.
• Readable Code: Use switch statements to make your code more readable and maintainable compared to multiple if-else statements.
• Java 12 Enhancements: As of Java 12, you can use switch expressions to return values directly from cases, simplifying the syntax and enhancing code readability.

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

public class SwitchEnumExample {
    public static void main(String[] args) {
        Day day = Day.WEDNESDAY;
        switch (day) {
            case MONDAY:
                System.out.println("Monday");
                break;
            case TUESDAY:
                System.out.println("Tuesday");
                break;
            case WEDNESDAY:
                System.out.println("Wednesday");
                break;
            case THURSDAY:
                System.out.println("Thursday");
                break;
            case FRIDAY:
                System.out.println("Friday");
                break;
            case SATURDAY:
                System.out.println("Saturday");
                break;
            case SUNDAY:
                System.out.println("Sunday");
                break;
        }
    }
}

Using enums in switch statements can enhance code readability and type safety.