Switch Case

What is switch statment?

• The switch keyword in Java is used to execute one block of code among many alternatives.

Syntax :
switch(expression){
case value1:
//code
break;
case value2:
//code
break;
...
...
default:
//default statment
}

• The expression is evaluated once and compared with the values of each case.
• If expression matches with value1, the code of case value1 are executed. Similarly, the code of case value2 is executed if expression matches with value2.
• If there is no match, the code of the default case is executed.

Which data types are supported in switch case expression?

• byte, short, int, char, String (since Java 7)

Not allowed:

• long,float,double,boolean

is it mandatory to use default statement in switch case in java?

• default is NOT mandatory in a Java switch. It is optional. We use it to handle unexpected values.

Why break statement is used?

• The break statement is used to terminate the switch-case statement. If break is not used, all the cases after the matching case are also executed.

What is fall-through in switch?

• Fall-through happens when a case block does not end with break, so execution continues into the next case block.

Can we have duplicate case values?

• No. Compiler error(duplicate case label).

Can we use expressions in case labels?

• No. Compiler error(constant expression required).

Example :

public class Sample {

    public static void main(String[] args)
    {
        char grade = 'B';
        switch(grade) {
            case 'A' :
                System.out.println("Excellent!");
                break;
            case 'B' :
            case 'C' :
                System.out.println("Well done");
                break;
            case 'D' :
                System.out.println("You passed");
                break;
            case 'F' :
                System.out.println("Better try again");
                break;
            default :
                System.out.println("Invalid grade");
       }

    }
}

What is the syntax of Switch case supported in java 12 and above?

• arrow (->) syntax.
• No need to add break statement to each case statement.

Example:

int mark = 50;
switch (mark) {
    case 90 -> "Monday";
    case 2 -> "Tuesday";
    case 3 -> "Wednesday";
    case 4 -> "Thursday";
    case 5 -> "Friday";
    case 6 -> "Saturday";
    case 7 -> "Sunday";
    default -> "Faile";
};
System.out.println(dayName); 
// Output: Wednesday

How to write multiple statement in a case block?

int day = 1;
switch (day) {
    case 1:
        System.out.println("Monday");
        System.out.println("Start of week");
        System.out.println("Go to work");
        break;
    case 2:
        System.out.println("Tuesday");
        break;
    default:
        System.out.println("Invalid day");
}

Java 12:

case 1 -> {
    System.out.println("Monday");
    System.out.println("Start of week");
}

How to write mutiple cases with same statement?

switch(day) {
    case 1:
    case 7:
        System.out.println("Holiday");
        System.out.println("Enjoy!");
        break;
}

Java 12:

case 1, 7 -> System.out.println("Weekend");