Switch Statements in Java

The switch statement in Java is a multi-way branch statement. In simple words, the Java switch statement executes one statement from multiple conditions.

It is an alternative to an if-else-if ladder statement. It provides an easy way to dispatch execution to different parts of code based on the value of the expression. The expression can be of type byte, short, char, int, long, enums, String, or wrapper classes (Integer, Short, Byte, Long).

Note: Java switch expression must be of byte, short, int, long(with its Wrapper type), enums and string. Beginning with JDK7, it also works with enumerated types (Enums in java), the String class, and Wrapper classes.

Syntax:

switch(expression)
{
  case value1 :
     // Statements
     break; // break is optional
  
  case value2 :
     // Statements
     break; // break is optional
     ....
     ....
     ....
   default : 
     // default Statement
}

Example: Size Printer Example

Java

public class SizePrinter {

    public static void main(String[] args) {
        int sizeNumber = 2; // Replace with your desired size (1, 2, 3, 4, or 5)

        switch (sizeNumber) {
            case 1:
                System.out.println("Extra Small");
                break;
            case 2:
                System.out.println("Small");
                break;
            case 3:
                System.out.println("Medium");
                break;
            case 4:
                System.out.println("Large");
                break;
            case 5:
                System.out.println("Extra Large");
                break;
            default:
                System.out.println("Invalid size number");
        }
    }
}

Output

Small

Some Important Rules for Java Switch Statements

• Case values must be constants or literals and of the same type as the switch expression.
• Duplicate case values are not allowed.
• The break statement is used to exit from the switch block. It is optional but recommended to prevent fall-through.
• The default case is optional and executes if no case matches the switch expression. It can appear anywhere within the switch block.

Note: Starting from Java 7, switch statements can use String type values. They can also handle wrapper classes like Integer, Short, Byte, Long.

Flowchart of Switch-Case Statement 

This flowchart shows the control flow and working of switch statements:

Note: Java switch statement is a fall through statement that means it executes all statements if break keyword is not used, so it is highly essential to use break keyword inside each case.  

Example: Finding Day

Consider the following Java program, it declares an int named day whose value represents a day(1-7). The code displays the name of the day, based on the value of the day, using the switch statement.

Java

// Java program to Demonstrate Switch Case
// with Primitive(int) Data Type

// Class
public class GFG {

    // Main driver method
    public static void main(String[] args)
    {
        int day = 5;
        String dayString;

        // Switch statement with int data type
        switch (day) {

        // Case
        case 1:
            dayString = "Monday";
            break;

        // Case
        case 2:
            dayString = "Tuesday";
            break;

            // Case
        case 3:
            dayString = "Wednesday";
            break;

            // Case
        case 4:
            dayString = "Thursday";
            break;

        // Case
        case 5:
            dayString = "Friday";
            break;

            // Case
        case 6:
            dayString = "Saturday";
            break;

            // Case
        case 7:
            dayString = "Sunday";
            break;

        // Default case
        default:
            dayString = "Invalid day";
        }
        System.out.println(dayString);
    }
}

Output

Friday

Break in switch case Statements

A break statement is optional. If we omit the break, execution will continue into the next case. 

It is sometimes desirable to have multiple cases without “break” statements between them. For instance, let us consider the updated version of the above program, it also displays whether a day is a weekday or a weekend day.

Example: Switch statement program without multiple breaks

Java

// Java Program to Demonstrate Switch Case
// with Multiple Cases Without Break Statements

// Class
public class GFG {

    // main driver method
    public static void main(String[] args)
    {
        int day = 2;
        String dayType;
        String dayString;

        // Switch case
        switch (day) {

        // Case
        case 1:
            dayString = "Monday";
            break;

        // Case
        case 2:
            dayString = "Tuesday";
            break;

            // Case
        case 3:
            dayString = "Wednesday";
            break;
        case 4:
            dayString = "Thursday";
            break;
        case 5:
            dayString = "Friday";
            break;
        case 6:
            dayString = "Saturday";
            break;
        case 7:
            dayString = "Sunday";
            break;
        default:
            dayString = "Invalid day";
        }

        switch (day) {
            // Multiple cases without break statements

        case 1:
        case 2:
        case 3:
        case 4:
        case 5:
            dayType = "Weekday";
            break;
        case 6:
        case 7:
            dayType = "Weekend";
            break;

        default:
            dayType = "Invalid daytype";
        }

        System.out.println(dayString + " is a " + dayType);
    }
}

Output

Tuesday is a Weekday

Java Nested Switch Statements

We can use a switch as part of the statement sequence of an outer switch. This is called a nested switch. Since a switch statement defines its block, no conflicts arise between the case constants in the inner switch and those in the outer switch.

Example: Nested Switch Statement

Java

// Java Program to Demonstrate
// Nested Switch Case Statement

// Class
public class GFG {

    // Main driver method
    public static void main(String[] args)
    {
        // Custom input string
        String Branch = "CSE";
        int year = 2;

        // Switch case
        switch (year) {

        // Case
        case 1:
            System.out.println(
                "elective courses : Advance english, Algebra");

            // Break statement to hault execution here
            // itself if case is matched
            break;

            // Case
        case 2:

            // Switch inside a switch
            // Nested Switch
            switch (Branch) {

            // Nested case
            case "CSE":
            case "CCE":
                System.out.println(
                    "elective courses : Machine Learning, Big Data");
                break;

            // Case
            case "ECE":
                System.out.println(
                    "elective courses : Antenna Engineering");
                break;

                // default case
                // It will execute if above cases does not
                // execute
            default:

                // Print statement
                System.out.println(
                    "Elective courses : Optimization");
            }
        }
    }
}

Output

elective courses : Machine Learning, Big Data

Java Enum in Switch Statement

Enums in Java are a powerful feature used to represent a fixed set of constants. They can be used in switch statements for better type safety and readability.

Example: Use of Enum in Switch

Java

// Java Program to Illustrate Use of Enum
// in Switch Statement

// Class
public class GFG {

    // Enum
    public enum Day { Sun, Mon, Tue, Wed, Thu, Fri, Sat }

    // Main driver method
    public static void main(String args[])
    {

        // Enum
        Day[] DayNow = Day.values();

        // Iterating using for each loop
        for (Day Now : DayNow) {

            // Switch case
            switch (Now) {

            // Case 1
            case Sun:
                System.out.println("Sunday");

                // break statement that hault further
                // execution once case is satisfied
                break;

            // Case 2
            case Mon:
                System.out.println("Monday");
                break;

            // Case 3
            case Tue:
                System.out.println("Tuesday");
                break;

            // Case 4
            case Wed:
                System.out.println("Wednesday");
                break;

            // Case 5
            case Thu:
                System.out.println("Thursday");
                break;

            // Case 6
            case Fri:
                System.out.println("Friday");
                break;

            // Case 7
            case Sat:
                System.out.println("Saturday");
            }
        }
    }
}

Output

Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday

Default statement in Java Switch Case

The default case in a switch statement specifies the code to run if no other case matches. It can be placed at any position in the switch block but is commonly placed at the end.

Example: Writing default in the middle of switch statements:

Java

import java.io.*;

class GFG {
    public static void main (String[] args) {
        int i=2;
          switch(i){
          default:
            System.out.println("Default");
          case 1:
            System.out.println(1);
            break;
          case 2:
            System.out.println(2);
          case 3:
            System.out.println(3);
        
        }
    }
}

Output

2
3

Example: Writing Default at the Beginning of Switch Statements

Java

import java.io.*;

class GFG {
    public static void main(String[] args)
    {
        int i = 5;
        switch (i) {
        default:
            System.out.println("Default");
        case 1:
            System.out.println(1);
            break;
        case 2:
            System.out.println(2);
        case 3:
            System.out.println(3);
        }
    }
}

Output

Default
1

Case label variations

Case labels and switch arguments can be constant expressions. The switch argument can be a variable expression but the case labels must be constant expressions.

Example: Using Variable in Switch Argument

Java

import java.io.*;

class GFG {
    public static void main(String[] args)
    {
        int x = 2;
        switch (x + 1) {
        case 1:
            System.out.println(1);
            break;
        case 1 + 1:
            System.out.println(2);
            break;
        case 2 + 1:
            System.out.println(3);
            break;
        default:
            System.out.println("Default");
        }
    }
}

Output

3

Example: Case Label Cannot Be Variable

A case label cannot be a variable or variable expression. It must be a constant expression.

Java

import java.io.*;

class GFG {
    public static void main(String[] args)
    {
        int x = 2;
        int y = 1;
        switch (x) {
        case 1:
            System.out.println(1);
            break;
        case 2:
            System.out.println(2);
            break;
        case x + y:
            System.out.println(3);
            break;
        default:
            System.out.println("Default");
        }
    }
}

./GFG.java:16: error: constant expression required
          case x+y:
                ^
1 error

Java Wrapper in Switch Statements

Java allows the use of wrapper classes (Integer, Short, Byte, Long, and Character) in switch statements. This provides flexibility when dealing with primitive data types and their corresponding wrapper types.

Example: Using Wrapper Classes

Java

public class WrapperSwitchExample {

    public static void main(String[] args) {
        Integer age = 25;

        switch (age) { // Extract primitive value for switch
            case 25:
                System.out.println("You are 25.");
                break;
            case 30:
                System.out.println("You are 30.");
                break;
            default:
                System.out.println("Age not matched.");
        }
    }
}

Output

You are 25.

Note: Regardless of its placement, the default case only gets executed if none of the other case conditions are met. So, putting it at the beginning, middle, or end doesn’t change the core logic (unless you’re using a less common technique called fall-through).

Example: Using Character Wrapper

Java

public class WrapperSwitchExample {
    public static void main(String[] args) {
        Character ch = 'c';

        switch (ch) { // Extract primitive value for switch
            case 'a':
                System.out.println("You are a.");
                break;
            case 'c':
                System.out.println("You are c.");
                break;
            default:
                System.out.println("Character not matched.");
        }
    }
}

Output

You are c.

Read More:

• Usage of Enum and Switch Keyword in Java
• String in Switch Case in Java
• Java Tutorial 

Exercise:

To practice Java switch statements you can visit the page: Java Switch Case statement Practice

Conclusion

Switch statements in Java are control flow structures that allow you to execute specific blocks of code based on the value of a single expression. They can be considered an alternative to if-else-if statements and are useful for handling multiple conditions in a clean and readable manner.

Java Switch Statements- FAQs

How to use switch statements in Java?

To use switch statement in Java, you can use the following syntax:

switch (expression) {
   case value1:
       // code to execute if expression equals value1
       break;
   case value2:
       // code to execute if expression equals value2
       break;
   // … more cases
   default:
       // code to execute if none of the above cases match
}

Can we pass null to a switch?

No, you can not pass NULL to a switch statement as they require constant expression in its case.

Can you return to a switch statement?

No, switch statements build a control flow in the program, so it can not go back after exiting a switch case.