Optional ifPresentOrElse() method in Java with examples

The ifPresentOrElse() method of the Optional class performs an action when a value is present and another action when the Optional is empty. It provides a convenient way to handle both cases without explicitly checking for the value.

• The method accepts a Consumer for handling a present value and a Runnable for handling an empty Optional.
• ifPresentOrElse() was introduced in Java 9.
• The method throws NullPointerException if the action is null when a value is present, or if the emptyAction is null when the Optional is empty.

Examples:

Input: Optional = Optional[9455]
Output: Value is present, its: 9455

Input: Optional = Optional.empty
Output: Value is empty

Syntax:

public void ifPresentOrElse(
Consumer<? super T> action,
Runnable emptyAction
)

1. Using ifPresentOrElse() with a Present Value

The following program creates an Optional containing an integer value. The Consumer action executes because the value is present.

import java.util.*;

public class GFG {
    public static void main(String[] args) {

        Optional<Integer> op = Optional.of(9455);

        System.out.println("Optional: " + op);

        op.ifPresentOrElse(
            value -> {
                System.out.println(
                    "Value is present, its: " + value);
            },
            () -> {
                System.out.println("Value is empty");
            }
        );
    }
}

Optional: Optional[9455]
Value is present, its: 9455

Explanation: The Optional contains 9455, so the Consumer action executes. The emptyAction is not executed because a value is present.

2. Using ifPresentOrElse() with an Empty Optional

The following program creates an empty Optional. The Runnable action executes because no value is present.

import java.util.*;

public class GFG {
    public static void main(String[] args) {

        Optional<Integer> op = Optional.empty();

        System.out.println("Optional: " + op);

        op.ifPresentOrElse(
            value -> {
                System.out.println(
                    "Value is present, its: " + value);
            },
            () -> {
                System.out.println("Value is empty");
            }
        );
    }
}

Optional: Optional.empty
Value is empty

Explanation: The Optional is empty, so the Runnable action executes and prints "Value is empty". The Consumer action is not executed because no value is present.

Note: NullPointerException is thrown when the required action is null.