Java Switch Expressions: Returning Values with Modern Switch Statements

Explore Java Switch Expressions, introduced in newer versions of Java, which allow you to return a value from a switch statement. Learn how to use the case L -> label and the yield statement to return values, improving the flexibility of switch statements.

Java - Switch Expressions

Switch expressions in Java allow us to return a value, making them usable within statements like other expressions. The case L -> label is used to return a value, or we can use the yield statement to return a value from the switch expression.

Introduction to Switch Expressions

Switch expressions were introduced as a preview feature in Java 12 and became standard in Java 14. Java 13 added the yield construct, which allows a switch expression to return a value.

Each case block in a switch expression can return a value using the yield statement. If using an enum, the default case can be skipped. Otherwise, a default case is required.

Switch Expression Using "case L ->" Labels

In Java, you can return a value from a switch expression using the case L -> notation.

Syntax


case label1, label2, ..., labeln -> expression;|throw-statement;|block;

Where label1 to labeln represent values to compare. If a label matches, the right-hand block after the arrow executes, and the result is returned.

Switch Expression Example: Using "case L ->" Labels

This example compares switch expressions with switch statements. The getDayType() method uses a switch expression, while getDayTypeOldStyle() uses a traditional switch statement.

Code


package com.tutorialsarena;

public class SwitchTester {
public static void main(String[] args) {
    System.out.println("Old Switch");
    System.out.println(getDayTypeOldStyle("Monday"));
    System.out.println(getDayTypeOldStyle("Saturday"));
    System.out.println(getDayTypeOldStyle("Invalid"));

    System.out.println("New Switch");
    System.out.println(getDayType("Monday"));
    System.out.println(getDayType("Saturday"));
    System.out.println(getDayType("Invalid"));   
}

public static String getDayType(String day) {
    return switch (day) {
        case "Monday", "Tuesday", "Wednesday", "Thursday", "Friday" -> "Weekday";
        case "Saturday", "Sunday" -> "Weekend";
        default -> "Invalid day.";
    };
}

public static String getDayTypeOldStyle(String day) {
    String result = null;
    switch (day) {
        case "Monday":
        case "Tuesday":
        case "Wednesday":
        case "Thursday":
        case "Friday":
        result = "Weekday";
        break;
        case "Saturday":
        case "Sunday":
        result = "Weekend";
        break;
        default:
        result = "Invalid day.";
    }
    return result;
}
}

Output


Old Switch
Weekday
Weekend
Invalid day.

New Switch
Weekday
Weekend
Invalid day.

Switch Expression Using "case L:" Statements and Yield

With the yield statement, a value can be returned from a switch expression or switch statement after performing an operation.

Syntax


case label1, label2, ..., labeln -> expression; yield value;
case label1: 
case labeln: expression; yield value;

Switch Expression Example: Using Yield Statement

In this example, the getDayType() method uses a switch expression with yield, while getDayTypeStyle2() uses the traditional case L: statement with yield.

Code


package com.tutorialsarena;

public class SwitchTester {
public static void main(String[] args) {
    System.out.println("Old Way");
    System.out.println(getDayTypeStyle2("Monday"));
    System.out.println(getDayTypeStyle2("Saturday"));

    System.out.println("New Way");
    System.out.println(getDayType("Monday"));
    System.out.println(getDayType("Saturday"));
    System.out.println(getDayType("Invalid"));
}

public static String getDayType(String day) {
    return switch (day) {
        case "Monday", "Tuesday", "Wednesday", "Thursday", "Friday" -> {
        System.out.println("In Weekdays");
        yield "Weekday";
        }
        case "Saturday", "Sunday" -> {
        System.out.println("In Weekends");
        yield "Weekend";
        }
        default -> throw new IllegalStateException("Invalid day: " + day);
    };
}

public static String getDayTypeStyle2(String day) {
    return switch (day) {
        case "Monday":
        case "Tuesday":
        case "Wednesday":
        case "Thursday":
        case "Friday":
        yield "Weekday";
        case "Saturday":
        case "Sunday":
        yield "Weekend";
        default:
        throw new IllegalStateException("Invalid day: " + day);
    };
}
}

Output


Old Way
Weekday
Weekend

New Way
In Weekdays
Weekday
In Weekends
Weekend
Exception in thread "main" java.lang.IllegalStateException: Invalid day: 
at com.tutorialsarena.SwitchTester.getDayType(SwitchTester.java:26)
at com.tutorialsarena.SwitchTester.main(SwitchTester.java:13)