Java 22 Unnamed Variables and Patterns Feature: A Concise Solution for Cleaner Coding

Java introduced a new feature, Unnamed Variables and Patterns (JEP 456), to handle situations where variables don't need to be explicitly named or identified. These cases often arise in exception handling and lambda expressions, where the identity of an individual variable is not crucial. Instead of declaring a variable with a specific name, we can simply use an underscore ( _ ) as a placeholder for these unnamed variables.

Let's understand this concept with some examples.

Handling Exceptions Using Named Variable In exception handling, we use a try-catch block to handle exceptions that may occur in our code. However, sometimes we catch an exception just to prevent our program from crashing, without needing to do anything with the exception object. In such cases, we don't need to explicitly declare the variable used to catch the exception. Instead, we can use the underscore (_) as a placeholder.

For instance, if we want to convert a String to an integer using the parseInt() method, but the string is not a valid number, the NumberFormatException will be caught by our try-catch block. In the first example, we use a named variable (exception) to catch the exception and print a message. In the second example, we use the underscore (_) as an unnamed variable, producing the same result.

package unnamedVariables;

public class Example1 {
    public static void main(String[] args) {
        try {
            int number = Integer.parseInt("231b");
        } catch (NumberFormatException exception) {
            System.out.println("Not a number");
        }
    }
}
‍

package unnamedVariables;

public class Example2 {
    public static void main(String[] args) {
        try {
            int number = Integer.parseInt("231b");
        } catch (NumberFormatException _) {
            System.out.println("Not a number");
        }
    }
}

Output: Not a number
‍

Lambda expressions are used to simplify coding in Java, especially when working with collections. Sometimes, we need to include a parameter in the lambda expression because of interface requirements, but we don't actually use it. In such cases, we can use the underscore (_) as a placeholder for the parameter, indicating that it is not important for our code. For example, if we want to iterate over a List of integers and print a message for each, we can use the forEach() method. In the first example, we use a named variable (integer) to iterate over the list and print a message. In the second example, we use the underscore (_) as an unnamed variable, producing the same result.

package unnamedVariables;

import java.util.Arrays;
import java.util.List;

public class Example3 {
    public static void main(String[] args) {
        List list = Arrays.asList(2, 4, 6, 9);
        list.forEach(integer -> System.out.println("This is an integer"));
    }
}
‍
‍

package unnamedVariables;

import java.util.Arrays;
import java.util.List;

public class Example4 {
    public static void main(String[] args) {
        List list = Arrays.asList(2, 4, 6, 9);
        list.forEach(_ -> System.out.println("This is an integer"));
    }
}

Output:
This is an integer
This is an integer
This is an integer
This is an integer
‍

‍Overall, Java's Unnamed Variables and Patterns feature helps us write more concise and readable code by eliminating the need for unnecessary variable declarations and naming. This results in cleaner and more efficient coding practices.

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