OptionalDouble ifPresentOrElse() method in Java with examples

The ifPresentOrElse(java.util.function.DoubleConsumer, java.lang.Runnable) method helps us to perform the specified DoubleConsumer action the value of this OptionalDouble object. If a value is not present in this OptionalDouble, then this method performs the given empty-based Runnable emptyAction, passed as the second parameter 

Syntax:

public void ifPresentOrElse(DoubleConsumer action,
                            Runnable emptyAction)

Parameters: This method accepts two parameters:

• action: which is the action to be performed on this Optional, if a value is present.
• emptyAction: which is the empty-based action to be performed, if no value is present.

Return value: This method returns nothing. 

Exception: This method throw NullPointerException if a value is present and the given action is null, or no value is present and the given empty-based action is null. 

Below programs illustrate ifPresentOrElse() method: 

Program 1:

Java

// Java program to demonstrate
// OptionalDouble.ifPresentOrElse() method

import java.util.OptionalDouble;

public class GFG {

    public static void main(String[] args)
    {

        // create a OptionalDouble
        OptionalDouble opdouble
            = OptionalDouble.of(234543.23453);

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

Output:

Value is present, its: 12

Program 2:

Java

// Java program to demonstrate
// OptionalDouble.ifPresentOrElse method
import java.util.OptionalDouble;

public class GFG {

    public static void main(String[] args)
    {

        // create a OptionalDouble
        OptionalDouble opdouble
            = OptionalDouble.empty();

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

Output:

Value is empty

References: https://docs.oracle.com/javase/10/docs/api/java/util/OptionalDouble.html#ifPresentOrElse(java.util.function.DoubleConsumer, java.lang.Runnable)