OBJECT ORIENTED PROGRAMMING THROUGH JAVA : Unit - 1 : Switch Statement

 

Java switch Statement

The switch statement in Java is a multi-branch conditional statement that executes one block of code out of many options based on the value of a variable or expression.

It is an alternative to using multiple if-else-if statements when checking for equality.

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Syntax of switch Statement

switch (expression) {
    case value1:
        // statements
        break;

    case value2:
        // statements
        break;

    ...

    default:
        // default statements
}

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🔑 Key Points:

• The expression must evaluate to one of the following types:

  • byte, short, int, char, String, or an enum

• case values must be unique constants or literals (not variables).

• break prevents fall-through (execution of the next case).

• default is optional and runs when no case matches.

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🔸 Example 1: Simple Day Selector

public class SwitchExample1 {
    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;

            default:
                System.out.println("Invalid Day");
        }
    }
}

📤 Output:
Wednesday

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🔸 Example 2: Switch with String

public class SwitchExample2 {
    public static void main(String[] args) {
        String fruit = "Mango";

        switch (fruit) {
            case "Apple":
                System.out.println("Apple is red.");
                break;

            case "Banana":
                System.out.println("Banana is yellow.");
                break;

            case "Mango":
                System.out.println("Mango is sweet.");
                break;

            default:
                System.out.println("Unknown fruit.");
        }
    }
}

📤 Output:
Mango is sweet.

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🔸 Example 3: Switch without break (Fall-through Behavior)

public class SwitchExample3 {
    public static void main(String[] args) {
        int number = 2;

        switch (number) {
            case 1:
                System.out.println("One");
            case 2:
                System.out.println("Two");
            case 3:
                System.out.println("Three");
            default:
                System.out.println("Default case");
        }
    }
}

📤 Output:

Two  
Three  
Default case

⚠️ Explanation: No break → executes all following cases.

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Example 4: Calculator using switch

import java.util.Scanner;

public class CalculatorSwitch {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter two numbers: ");
        double a = sc.nextDouble();
        double b = sc.nextDouble();

        System.out.print("Enter operation (+, -, *, /): ");
        char op = sc.next().charAt(0);

        switch (op) {
            case '+':
                System.out.println("Result = " + (a + b));
                break;

            case '-':
                System.out.println("Result = " + (a - b));
                break;

            case '*':
                System.out.println("Result = " + (a * b));
                break;

            case '/':
                if (b != 0)
                    System.out.println("Result = " + (a / b));
                else
                    System.out.println("Division by zero not allowed.");
                break;

            default:
                System.out.println("Invalid operator.");
        }

        sc.close();
    }
}

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