Java Switch Statement

The java switch statement can have a number of possible execution paths. A switch works with the byte, short, char , and int primitive data types. It also works with enumerated types, the String class, and a few special classes that wrap certain primitive types: Character, Byte, Short, and Integer

In simple word switch case statement is used when we have number of options (or choices) and we may need to perform a different task for each choice.

Syntax:

switch(expression){
    case value1:
    // statement or code to be executed;
    break; // optional
    case value2:
    // statement or code to be executed;
    break; // optional
    case value3:
    // statement or code to be executed;
    break; // optional
    ...
    ...
    ...
    default:
    // if all cases are not matched then this code to be executed;
}

Some Important points/rule should be followed when we use switch statements:

1. Duplicate case values are not allowed.

2. The value for a case must be a literal or a constant. Variables are not allowed.

3. The value for a all cases must be of the same data type as the variable in the switch.

Example: The code displays the name of the month, based on the value of month, using the switch statement.

class Simple{
    public static void main(String args[]){

    int month = 4;
    String monthString;

    switch(month){
        case 1:   monthString = "January";
        break;
        case 2:   monthString = "February";
        break;
        case 3:   monthString = "March";
        break;
        case 4:   monthString = "April";
        break;
        case 5:   monthString = "May";
        break;
        case 6:   monthString = "June";
        break;
        case 7:   monthString = "July";
        break;
        case 8:   monthString = "August";
        break;
        case 9:   monthString = "September";
        break;
        case 10:   monthString = "October";
        break;
        case 11:   monthString = "November";
        break;
        case 12:   monthString = "December";
        break;
        default:   monthString = "Invalid month";
        break;
        }
        System.out.println(monthString);
    }
}

Output:

April

Example: The code displays the Decimal to hexaDecimal

class Simple{
    public static void main(String args[]){
    int digitInDecimal = 12;
    switch(digitInDecimal){
        case 0:
        System.out.println("0");
        break;
        case 1:
        System.out.println("1");
        break;
        case 2:
        System.out.println("2");
        break;
        case 3:
        System.out.println("3");
        break;
        case 4:
        System.out.println("4");
        break;
        case 5:
        System.out.println("5");
        break;
        case 6:
        System.out.println("6");
        break;
        case 7:
        System.out.println("7");
        break;
        case 8:
        System.out.println("8");
        break;
        case 9:
        System.out.println("9");
        break;
        case 10:
        System.out.println("A");
        break;
        case 11:
        System.out.println("B");
        break;
        case 12:
        System.out.println("C");
        break;
        case 13:
        System.out.println("D");
        break;
        case 14:
        System.out.println("E");
        break;
        case 15:
        System.out.println("F");
        break;
        default:
        System.out.println("Invalid");
        break;
        }
    }
}

Output:

C

Using Strings in switch Statements

In Java SE 7 and later, you can use a String object in the switch statement's expression. The case statement should be string literal.

Example:

class Simple{
    public static void main(String args[]){
    String dayString = "Sunday";
    int dayNumber;
    switch(dayString){
        case "monday":
            dayNumber = 1;
            break;
        case "Tuesday":
            dayNumber = 2;
            break;
        case "Wednesday":
            dayNumber = 3;
            break;
        case "Thursday":
            dayNumber = 4;
            break;
        case "Friday":
            dayNumber = 5;
            break;
        case "Saturday":
            dayNumber = 6;
            break;
        case "Sunday":
            dayNumber = 7;
            break;
        default:   dayNumber = 0;
            break;
        }
        System.out.println(dayNumber);
    }
}

Output:

7