Java 8 – Provide Default Value Using Optional

Introduction

In Java, dealing with null values is a common challenge, often leading to NullPointerException. Java 8 introduced the Optional class to help developers manage null values more gracefully. One of the key features of Optional is its ability to provide a default value when the Optional is empty. This approach allows you to write more robust code by avoiding null checks and ensuring that a valid value is always returned.

In this guide, we’ll explore how to use Optional to provide default values in Java 8, covering different scenarios where this technique can be applied.

Table of Contents

• Problem Statement
• Solution Steps
• Java Program
  • Example 1: Using Optional.orElse() for a Default Value
  • Example 2: Using Optional.orElseGet() for a Supplier-Based Default Value
  • Example 3: Using Optional.orElseThrow() to Throw an Exception
• Conclusion

Problem Statement

When working with objects that might be null, you often need to ensure that a default value is provided if the object is absent. The goal is to use Optional in Java 8 to provide a default value, ensuring that the code doesn’t throw NullPointerException and that a valid value is always returned.

Example:

• Problem: Returning null or handling null values can lead to errors or require extensive null checks.
• Goal: Use Optional to provide default values in a clean and effective way.

Solution Steps

1. Provide a Default Value: Use Optional.orElse() to return a default value if the Optional is empty.
2. Generate a Default Value Lazily: Use Optional.orElseGet() to generate a default value only when needed, using a Supplier.
3. Throw an Exception if Absent: Use Optional.orElseThrow() to throw an exception if the value is not present, handling error cases explicitly.

Java Program

Example 1: Using Optional.orElse() for a Default Value

The orElse() method provides a default value if the Optional is empty.

import java.util.Optional;

/**
 * Java 8 - Provide Default Value Using Optional
 * Author: https://www.rameshfadatare.com/
 */
public class OptionalExample1 {

    public static void main(String[] args) {
        Optional<String> optionalName = Optional.empty();

        // Provide a default value if the Optional is empty
        String name = optionalName.orElse("Default Name");
        System.out.println("Name: " + name);
    }
}

Output

Name: Default Name

Explanation

• Optional.orElse(): Returns the contained value if present; otherwise, it returns the specified default value. This method is useful when you want to ensure that a non-null value is always returned.

Example 2: Using Optional.orElseGet() for a Supplier-Based Default Value

The orElseGet() method is similar to orElse(), but it uses a Supplier to provide the default value, which is only executed if the Optional is empty.

import java.util.Optional;

/**
 * Java 8 - Provide Default Value Using Optional
 * Author: https://www.rameshfadatare.com/
 */
public class OptionalExample2 {

    public static void main(String[] args) {
        Optional<String> optionalName = Optional.empty();

        // Provide a default value using a Supplier if the Optional is empty
        String name = optionalName.orElseGet(() -> "Generated Default Name");
        System.out.println("Name: " + name);
    }
}

Output

Name: Generated Default Name

Explanation

• Optional.orElseGet(): Similar to orElse(), but the default value is generated by a Supplier only when needed. This is beneficial when the default value is expensive to compute, as it avoids unnecessary computation if the value is present.

Example 3: Using Optional.orElseThrow() to Throw an Exception

The orElseThrow() method throws an exception if the Optional is empty. This approach is useful when the absence of a value is considered an error that should be explicitly handled.

import java.util.Optional;

/**
 * Java 8 - Provide Default Value Using Optional
 * Author: https://www.rameshfadatare.com/
 */
public class OptionalExample3 {

    public static void main(String[] args) {
        Optional<String> optionalName = Optional.empty();

        // Throw an exception if the Optional is empty
        try {
            String name = optionalName.orElseThrow(() -> new IllegalArgumentException("Name not found"));
            System.out.println("Name: " + name);
        } catch (Exception e) {
            System.err.println(e.getMessage());
        }
    }
}

Output

Name not found

Explanation

• Optional.orElseThrow(): Throws a specified exception if the Optional is empty. This method is useful when you need to enforce the presence of a value and handle cases where it is absent with a specific exception.

Conclusion

Using Optional in Java 8 to provide default values is a powerful way to handle potentially null values in a more controlled and expressive manner. By using methods like orElse(), orElseGet(), and orElseThrow(), you can ensure that your code is robust, avoids NullPointerException, and handles absent values gracefully. Whether you need to return a default value, lazily generate one, or throw an exception, Optional provides a clean and efficient solution to manage these scenarios.