switch-case Statement

The switch statement is a control structure used to perform multi-way branching based on the value of a specific variable or expression. Unlike if statements, which can handle complex conditions, a switch statement is ideal for scenarios where you need to compare a variable against multiple specific values, allowing for a cleaner, more readable structure for certain types of code.

Basic Syntax of switch Statement

The basic syntax of a switch statement is as follows:

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

• expression is evaluated once and compared to each case value.
• Each case represents a specific value to compare against.
• break is used to exit the switch block after a matching case executes, preventing “fall-through” (where code continues executing subsequent cases).
• default is optional and runs if no other case matches. It acts as a catch-all similar to an else in an if-else structure.

Example of a switch Statement

int day = 3;
String dayName;

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

System.out.println("The day is: " + dayName);

In this example, dayName will be set to "Wednesday" because day has a value of 3.

Important Points about switch Statement

• Data Types Supported: The switch statement in Java can handle int, char, String, enum, and short.
• Fall-Through: If a case does not end with break, control “falls through” to the next case, which may lead to unintended results.
• Using default Case: Including the default case is generally recommended, even if you think all possible cases are covered, to handle unexpected values.

Advanced Example with switch

In this example, a switch statement processes different commands.

String command = "start";

switch (command) {
    case "start":
        System.out.println("System is starting...");
        break;
    case "stop":
        System.out.println("System is stopping...");
        break;
    case "restart":
        System.out.println("System is restarting...");
        break;
    default:
        System.out.println("Unknown command");
        break;
}

Enhanced switch Expressions (Java 12+)

Starting from Java 12, switch can be used as an expression, which allows for more concise code:

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 day";
};
System.out.println("The day is: " + dayName);

In this example, the switch expression directly returns a value, making the code cleaner and removing the need for break statements.

When to Use switch vs if-else

• Use switch when you have multiple specific values to check, especially with int, char, String, or enum.
• Use if-else for complex conditions or ranges (e.g., if (x > 10 && y < 20)).