Retrieving the First Non-Null Value in Java

In Java development, handling null values effectively is crucial for robust and error-free code. Often, there is a need to retrieve the first non-null value from a set of variables or expressions. This scenario is common in applications with multiple fallbacks or default values. In this blog post, we'll explore various methods to find the first non-null value in Java, ensuring code reliability and readability. 

Understanding the Need for Non-Null Values 

Finding the first non-null value is essential in scenarios where multiple potential values are available, and you want to use the first available valid one. This situation arises frequently in settings like configurations, user inputs, or data fetched from multiple sources. 

Different Ways to Get the First Non-Null Value 

Method 1: Traditional Approach using Conditional Checks 

The most straightforward method is to use a series of if statements to check each value and return the first non-null one. 

public class NonNullFinder {
    public static void main(String[] args) {
        String a = null;
        String b = null;
        String c = "Hello, World!";

        String firstNonNull = a != null ? a : (b != null ? b : c);
        System.out.println("First non-null value: " + firstNonNull);
    }
}

Output:

First non-null value: Hello, World!

Method 2: Using Java 8's Optional API 

Java 8 introduced Optional, a container object that may or may not contain a non-null value. The Optional class provides methods like ofNullable and orElse which can be used to streamline finding the first non-null value. 

import java.util.Optional;

public class NonNullFinder {
    public static void main(String[] args) {
        String a = null;
        String b = null;
        String c = "Hello, World!";

        String firstNonNull = Optional.ofNullable(a)
                                      .orElse(Optional.ofNullable(b)
                                                      .orElse(c));
        System.out.println("First non-null value: " + firstNonNull);
    }
}

Output:

First non-null value: Hello, World!

This method is more elegant and works well with a small number of variables. 

Method 3: Using Apache Commons Lang 

If you're using the Apache Commons Lang library, you can utilize the ObjectUtils.firstNonNull() method. This method simplifies the process, especially with multiple values. 

import org.apache.commons.lang3.ObjectUtils;

public class NonNullFinder {
    public static void main(String[] args) {
        String a = null;
        String b = null;
        String c = "Hello, World!";

        String firstNonNull = ObjectUtils.firstNonNull(a, b, c);
        System.out.println("First non-null value: " + firstNonNull);
    }
}

Output:

First non-null value: Hello, World!

Apache Commons Lang provides a clean and concise way to achieve this with minimal code. 

Method 4: Using Stream API 

For a more functional approach, especially with a collection of values, the Stream API can be effectively used. 

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

public class NonNullFinder {
    public static void main(String[] args) {
        List<String> values = Arrays.asList(null, null, "Hello, World!");

        String firstNonNull = values.stream()
                                    .filter(java.util.Objects::nonNull)
                                    .findFirst()
                                    .orElse(null);
        System.out.println("First non-null value: " + firstNonNull);
    }
}

Output:

First non-null value: Hello, World!

Conclusion 

Retrieving the first non-null value is a common requirement in Java. Depending on the context and the number of values you're dealing with, you can choose the traditional approach, Java 8's Optional API, external libraries like Apache Commons Lang, or the Stream API for an elegant solution. 

Understanding these techniques is valuable for Java developers to write more concise, readable, and robust code. Stay tuned for more Java programming tips and best practices. Happy coding!