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Java switch Statement

How to write Java switch Statement

The switch statement in Java allows you to execute one block of code among many alternatives. It’s a cleaner and more readable alternative to using multiple if-else conditions when testing the same variable against several values.

1. Syntax of switch

switch (expression) {
    case value1:
        // Code to execute if expression equals value1
        break; // Optional, but necessary to prevent fall-through
    case value2:
        // Code to execute if expression equals value2
        break;
    // Add more cases as needed
    default:
        // Code to execute if expression doesn't match any case
}
  • The expression inside the switch statement is evaluated once, and the value of the expression is compared with each case value.
  • If a match is found, the corresponding block of code is executed.
  • The break keyword is used to exit the switch statement, preventing the execution from falling through to subsequent cases.
  • The default block is optional and runs if no case matches.

2. Example of a switch Statement

public class Main {
    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");  // Outputs: Wednesday
                break;
            case 4:
                System.out.println("Thursday");
                break;
            case 5:
                System.out.println("Friday");
                break;
            default:
                System.out.println("Weekend");
        }
    }
}

In this example, since day is 3, the code inside the case 3: block is executed, printing "Wednesday" to the console.

3. break Statement

In a switch statement, the break statement is crucial. Without it, the code will continue to execute the subsequent cases, even if a match has already been found. This is known as fall-through behavior.

Example Without break:

public class Main {
    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");  // Outputs: Wednesday
            case 4:
                System.out.println("Thursday");   // Also prints this
            case 5:
                System.out.println("Friday");     // And this
            default:
                System.out.println("Weekend");    // And this
        }
    }
}

In this case, without the break statements, Java will execute all the cases starting from the matched case (case 3) until the end of the switch block, leading to unexpected output.

4. default Case

The default case in a switch statement is optional and will be executed if none of the case values match the expression. It acts as a fallback for unmatched cases.

Example:

public class Main {
    public static void main(String[] args) {
        int day = 7;

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

Here, since day is 7 and there is no case for 7, the default block is executed, printing "Invalid day".

5. Multiple Case Labels

You can group multiple case labels together if they should execute the same block of code. This is useful for conditions where multiple values have the same outcome.

Example:

public class Main {
    public static void main(String[] args) {
        int day = 6;

        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");  // Outputs: Weekend
                break;
        }
    }
}

In this example, both case 6 and case 7 will print "Weekend" to the console.

6. Data Types Supported by switch

The switch statement in Java supports the following data types:

  • byte, short, int, char: The most common types used in switch statements.
  • String: Since Java SE 7, you can use String in switch expressions.
  • enum: You can also use enum constants in a switch statement.

7. Using switch with Strings

Since Java SE 7, you can use a String expression in a switch statement, making it easier to work with text-based conditions.

Example:

public class Main {
    public static void main(String[] args) {
        String day = "Tuesday";

        switch (day) {
            case "Monday":
                System.out.println("Start of the week");
                break;
            case "Tuesday":
                System.out.println("Second day of the week");  // Outputs: Second day of the week
                break;
            case "Wednesday":
                System.out.println("Midweek");
                break;
            default:
                System.out.println("Unknown day");
        }
    }
}

Here, the expression is a String, and the switch statement compares the value of day to each case string.

8. Example with enum Type

You can also use enum types in a switch statement. An enum is a special data type that represents a group of constants.

Example:

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

public class Main {
    public static void main(String[] args) {
        Day day = Day.WEDNESDAY;

        switch (day) {
            case MONDAY:
                System.out.println("Start of the week");
                break;
            case WEDNESDAY:
                System.out.println("Midweek");  // Outputs: Midweek
                break;
            case FRIDAY:
                System.out.println("End of the workweek");
                break;
            default:
                System.out.println("Weekend");
        }
    }
}

In this example, the enum type Day is used in the switch statement, making it easy to handle specific days of the week.

9. Summary

  • The switch statement is a cleaner alternative to using multiple if-else conditions when testing the same variable.
  • Always use break to prevent fall-through behavior.
  • The default case handles unmatched conditions.
  • You can use int, char, String, enum, and other primitive data types in switch statements.
  • Grouping case labels allows for multiple conditions to execute the same block of code.

By using switch, you can make your code more organized and easier to read, especially when working with multiple conditions based on a single expression.

Java switch Statement

How to write Java switch Statement

The switch statement in Java allows you to execute one block of code among many alternatives. It’s a cleaner and more readable alternative to using multiple if-else conditions when testing the same variable against several values.

1. Syntax of switch

switch (expression) {
    case value1:
        // Code to execute if expression equals value1
        break; // Optional, but necessary to prevent fall-through
    case value2:
        // Code to execute if expression equals value2
        break;
    // Add more cases as needed
    default:
        // Code to execute if expression doesn't match any case
}
  • The expression inside the switch statement is evaluated once, and the value of the expression is compared with each case value.
  • If a match is found, the corresponding block of code is executed.
  • The break keyword is used to exit the switch statement, preventing the execution from falling through to subsequent cases.
  • The default block is optional and runs if no case matches.

2. Example of a switch Statement

public class Main {
    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");  // Outputs: Wednesday
                break;
            case 4:
                System.out.println("Thursday");
                break;
            case 5:
                System.out.println("Friday");
                break;
            default:
                System.out.println("Weekend");
        }
    }
}

In this example, since day is 3, the code inside the case 3: block is executed, printing "Wednesday" to the console.

3. break Statement

In a switch statement, the break statement is crucial. Without it, the code will continue to execute the subsequent cases, even if a match has already been found. This is known as fall-through behavior.

Example Without break:

public class Main {
    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");  // Outputs: Wednesday
            case 4:
                System.out.println("Thursday");   // Also prints this
            case 5:
                System.out.println("Friday");     // And this
            default:
                System.out.println("Weekend");    // And this
        }
    }
}

In this case, without the break statements, Java will execute all the cases starting from the matched case (case 3) until the end of the switch block, leading to unexpected output.

4. default Case

The default case in a switch statement is optional and will be executed if none of the case values match the expression. It acts as a fallback for unmatched cases.

Example:

public class Main {
    public static void main(String[] args) {
        int day = 7;

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

Here, since day is 7 and there is no case for 7, the default block is executed, printing "Invalid day".

5. Multiple Case Labels

You can group multiple case labels together if they should execute the same block of code. This is useful for conditions where multiple values have the same outcome.

Example:

public class Main {
    public static void main(String[] args) {
        int day = 6;

        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");  // Outputs: Weekend
                break;
        }
    }
}

In this example, both case 6 and case 7 will print "Weekend" to the console.

6. Data Types Supported by switch

The switch statement in Java supports the following data types:

  • byte, short, int, char: The most common types used in switch statements.
  • String: Since Java SE 7, you can use String in switch expressions.
  • enum: You can also use enum constants in a switch statement.

7. Using switch with Strings

Since Java SE 7, you can use a String expression in a switch statement, making it easier to work with text-based conditions.

Example:

public class Main {
    public static void main(String[] args) {
        String day = "Tuesday";

        switch (day) {
            case "Monday":
                System.out.println("Start of the week");
                break;
            case "Tuesday":
                System.out.println("Second day of the week");  // Outputs: Second day of the week
                break;
            case "Wednesday":
                System.out.println("Midweek");
                break;
            default:
                System.out.println("Unknown day");
        }
    }
}

Here, the expression is a String, and the switch statement compares the value of day to each case string.

8. Example with enum Type

You can also use enum types in a switch statement. An enum is a special data type that represents a group of constants.

Example:

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

public class Main {
    public static void main(String[] args) {
        Day day = Day.WEDNESDAY;

        switch (day) {
            case MONDAY:
                System.out.println("Start of the week");
                break;
            case WEDNESDAY:
                System.out.println("Midweek");  // Outputs: Midweek
                break;
            case FRIDAY:
                System.out.println("End of the workweek");
                break;
            default:
                System.out.println("Weekend");
        }
    }
}

In this example, the enum type Day is used in the switch statement, making it easy to handle specific days of the week.

9. Summary

  • The switch statement is a cleaner alternative to using multiple if-else conditions when testing the same variable.
  • Always use break to prevent fall-through behavior.
  • The default case handles unmatched conditions.
  • You can use int, char, String, enum, and other primitive data types in switch statements.
  • Grouping case labels allows for multiple conditions to execute the same block of code.

By using switch, you can make your code more organized and easier to read, especially when working with multiple conditions based on a single expression.