Java 8 Optional Class

Java 8 introduced the Optional class to represent a value that may or may not be present. It provides a clear way to handle missing values instead of relying directly on null.

• Provides methods to check, retrieve, transform, or provide alternatives for a value.
• Encourages explicit handling of potentially absent values.

Why Do We Need Optional?

Using null to represent a missing value requires explicit null checks. If these checks are missed, accessing the value can result in a NullPointerException. Optional makes the possibility of an absent value explicit and provides methods for handling both present and empty cases.

Example: Program Without the Optional Class

public class OptionalDemo {
    public static void main(String[] args)
    {
        String[] words = new String[10];
        String word = words[5].toLowerCase();
        System.out.print(word);
    }
}

Output:

Exception in thread "main" java.lang.NullPointerException

To avoid abnormal termination, we use the Optional class. In the following example, we are using Optional. So, our program can execute without crashing.

Example: Program using Optional Class

import java.util.Optional;

// Driver Class
public class OptionalDemo {
      // Main Method
    public static void main(String[] args)
    {
        String[] words = new String[10];
        
          Optional<String> checkNull = Optional.ofNullable(words[5]);
        
          if (checkNull.isPresent()) {
            String word = words[5].toLowerCase();
            System.out.print(word);
        }
        else
            System.out.println("word is null");
    }
}

word is null

Creating Optional Objects

The Optional class provides factory methods to create objects based on whether a value is available or may be absent.

• Optional.empty(): Creates an Optional that contains no value.
• Optional.of(value): Creates an Optional with a non-null value. It throws NullPointerException if the value is null.
• Optional.ofNullable(value): Creates an Optional containing the value if it is non-null; otherwise, returns an empty Optional.

Example 1: Using empty() and of()

import java.util.Optional;

class GFG {
    public static void main(String[] args) {
        String[] str = new String[5];
        str[2] = "Geeks Classes are coming soon";

        Optional<String> empty = Optional.empty();
        System.out.println(empty); 

        Optional<String> value = Optional.of(str[2]);
        System.out.println(value); 
    }
}

Optional.empty
Optional[Geeks Classes are coming soon]

Explanation: In this example, Optional.empty() creates an Optional object with no value. Then, Optional.of(str[2]) creates an Optional that contains a non-null string. The print statements display an empty Optional and an Optional holding a value, showing how Optional safely represents both cases.

Example 2: Using get(), hashCode() and isPresent()

import java.util.Optional;

class GFG {
    public static void main(String[] args) {
        String[] str = new String[5];
        str[2] = "Geeks Classes are coming soon";

        Optional<String> value = Optional.of(str[2]);

        System.out.println(value.get());       
        System.out.println(value.hashCode());  
        System.out.println(value.isPresent()); 
    }
}

Geeks Classes are coming soon
1967487235
true

Explanation: Here, Optional.of(str[2]) stores a value inside the Optional object. The get() method retrieves that value, hashCode() returns its hash value, and isPresent() checks whether a value exists. Since the value is present, it returns true.

Common Methods in Optional

The Optional class offers methods such as isPresent() orElse() and ifPresent() to handle potentially null values more safely and functionally. The table below lists commonly used Optional methods and their descriptions.