Pattern Matching for Switch

The pattern matching regarding the switch statements was introduced in the Java 12 version and later introduced as a standard feature in the Java 13 version. Let's understand about pattern matching for switch in Java in detail in the following paragraphs.

The main purpose of it was to make the readability of the code simpler and introduce a simple and expressive technique for performing pattern matching check between the statements of switch keyword in Java.

Pattern Matching for Switch in Java

Previously in Java, the statements of switch keyword were held withing simple equality checks using either constants or primitive data types. In Java, the switch statement gains lot of flexibility by introducing the pattern matching as it allows users and developers for using pattern for matching complex objects and data structures.

One of the major benefits of using pattern matching for switch keyword in Java is that it provides the ability for removing the boilerplate code. In situations where several if-else statements or nested instanceOf statements are followed by explicit type of casting, the users or developers can create simple and understandable. With the usage of pattern matching for switch in Java, the code becomes more streamlined and least prone to errors.

Syntax for Pattern Matching in Switch Statements

The syntax utilized for pattern matching in switch statements in Java consists the utilization of the case keyword which must be followed by a pattern. The patterns mentioned previously may contain several types of elements, such as patterns of type which checks the object's type.

Let's understand about the pattern matching in switch statements in Java with the help of an example program.

Example 1:

It is a traditional syntax or approach of using switch statement in Java and it includes the usage of keywords switch, case, default, and break.

Filename: PatternMatchingSwitch.java

import java.io.*;
public class PatternMatchingSwitch {
    public static void main(String[] args) {
        int number = 2; // Initializing an integer value named number with a value of 2
        String answer; // Declaring a String variable named answer
        switch (number) { // Starting a switch statement using the value of number as the input
            case 1: // If number is equal to 1, execute the code below
                answer = "The number is One"; // Set answer to the String "One"
                break; // Exit the switch statement
            case 2: // If number is equal to 2, execute the code below
                answer = "The number is Two"; // Set answer to the String "Two"
                break; // Exit the switch statement
            case 3: // If number is equal to 3, execute the code below
                answer = "The number is Three"; // Set answer to the String "Three"
                break; // Exit the switch statement
            default: // If none of the above cases match, execute the code below
                answer = "The number is Unknown"; // Set answer to the String "Unknown"
                break; // Exit the switch statement
        }
        // Displaying the value of the answer to the console
        System.out.println(answer);
    }
}

Output:

The number is Two

Example 2:

It is a lambda syntax or approach of using switch statement.

Filename: PatterMatching1.java

import java.io.*; 
public class PatterMatching1 { 
	public static void main(String[] args) 
	{ 
		// Assigning the value of the Day_Of_Week variable to 3 
		int Day_Of_Week = 5; 
		// Utilizing a switch statement for determining the name of the Day_Of_Week of the week 
		switch (Day_Of_Week) { 
		case 1 ->System.out.println("Today is Monday"); // If Day_Of_Week equals 1, print "MonDay_Of_Week" 
		case 2 ->System.out.println("Today is Tuesday"); // If Day_Of_Week equals 2, print "TuesDay_Of_Week" 
		case 3 ->System.out.println("Today is Wednesday");// If Day_Of_Week equals 3, print "WednesDay_Of_Week" 
		case 4 ->System.out.println("Today is Thursday"); // If Day_Of_Week equals 4, print "ThursDay_Of_Week" 
		case 5 ->System.out.println("Today is Friday"); // If Day_Of_Week equals 5, print "FriDay_Of_Week" 
		case 6 ->System.out.println("Today is Saturday"); // If Day_Of_Week equals 6, print "SaturDay_Of_Week" 
		case 7 ->System.out.println("Today is Sunday"); // If Day_Of_Week equals 7, print "SunDay_Of_Week" 
		default ->System.out.println("Invalid Day"); // If Day_Of_Week is not in the range 1-7, print "Invalid Day_Of_Week" 
		} 
	} 
}

Output:

Today is Friday

Let's understand in detail about pattern matching in switch keyword in Java by taking an example of matching on strings.

Example 3:

This is a traditional syntax or approach of using switch keyword in Java.

Filename: PatterMatching2.java

import java.io.*;
public class PatterMatching2 {
    public static void main(String args[]) {
        // Creating a string variable named "fruit_variable" and initialize it to
        // "banana"
        String fruit_variable = "banana";
        // Utilizing a switch statement to determine the value of the "fruit_variable" variable
        switch (fruit_variable) {
            // If the value of "fruit_variable" is
            // "apple", execute this case
            case "apple":
                System.out.println("The fruit is an apple.");
                break;
            // If the value of "fruit_variable" is
            // "banana", execute this case
            case "banana":
                System.out.println("The fruit is a banana.");
                break;
            // If the value of "fruit_variable" is "orange",
            // execute this case
            case "orange":
                System.out.println("The fruit is an orange.");
                break;
            // If the value of "fruit_variable" is not "apple",
            // "banana", or "orange", execute this case
            default:
                System.out.println("The fruit is not an apple, banana, or orange.");
        }
    }
}

Output:

The fruit is a banana.

Let's look at another example that works on matching on constants of Enum in Java.

Filename: PatternMatching3.java

import java.io.*; 
public class PatternMatching3 { 
	public static void main(String[] args) 
	{ 
		enum colors { RED, GREEN, BLUE } 
		colors color_variable = colors.RED; 
		// Matching on the enum constant "color_variable" 
		switch (color_variable) { 
		// Matching on the enum constant "RED" 
		case RED -> System.out.println("The Color is red."); 
		// Matching on the enum constant "GREEN" 
		case GREEN -> System.out.println("The Color is green."); 
		// Matching on the enum constant "BLUE" 
		case BLUE -> System.out.println("The Color is blue."); 
		} 
	} 
}

Output: