Difference Between ifPresent() and ifPresentOrElse() in Optional

Both methods belong to the Optional<T> class and are used to handle optional values in Java.

ifPresent() (Java 8)

• Executes a provided action only if the Optional contains a value.
• Does nothing if the Optional is empty.

Example: Using ifPresent()

import java.util.Optional;

public class IfPresentExample {
    public static void main(String[] args) {
        Optional optionalValue = Optional.of("Java 8");

        optionalValue.ifPresent(value -> System.out.println("Value: " + value));
    }
}

Output:

Value: Java 8

If the value is present, it prints it; otherwise, it does nothing.

ifPresentOrElse() (Java 9)

• Executes a provided action if the Optional contains a value.
• Executes a different action if the Optional is empty.

Example: Using ifPresentOrElse()

import java.util.Optional;

public class IfPresentOrElseExample {
    public static void main(String[] args) {
        Optional optionalValue = Optional.of("Java 9");

        optionalValue.ifPresentOrElse(
            value -> System.out.println("Value: " + value), 
            () -> System.out.println("No value present")
        );

        Optional emptyOptional = Optional.empty();

        emptyOptional.ifPresentOrElse(
            value -> System.out.println("Value: " + value), 
            () -> System.out.println("No value present")
        );
    }
}

Output:

Value: Java 9
No value present

Executes the first lambda if present, otherwise runs the second lambda.

Key Differences

When to Use What?

• Use ifPresent() → When you only care about the presence of a value.
• Use ifPresentOrElse() → When you want to handle both presence and absence.

Example: Handling Database Lookup

import java.util.Optional;

public class UserService {
    public static void main(String[] args) {
        Optional user = findUserById(1);

        user.ifPresentOrElse(
            name -> System.out.println("User found: " + name),
            () -> System.out.println("User not found")
        );
    }

    public static Optional findUserById(int id) {
        return id == 1 ? Optional.of("John Doe") : Optional.empty();
    }
}

Output (if user exists):

User found: John Doe

Output (if user doesn’t exist):

User not found

Best for handling database lookups, APIs, and missing values gracefully.

Summary

• ifPresent() → Performs an action if the value exists, does nothing otherwise.
• ifPresentOrElse() → Handles both cases: executes an action if present, a fallback if absent.
• ifPresentOrElse() is more flexible but requires Java 9+.