OptionalDouble ifPresent(DoubleConsumer) method in Java with examples

The ifPresent(java.util.function.DoubleConsumer) 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 does nothing. 

Syntax:

public void ifPresent(DoubleConsumer action)

Parameters: This method accepts a parameter action which is the action to be performed on this Optional, if a 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. 

Below programs illustrate ifPresent(DoubleConsumer) method: 

Program 1:

Java

// Java program to demonstrate
// OptionalDouble.ifPresent(DoubleConsumer) method

import java.util.OptionalDouble;

public class GFG {

    public static void main(String[] args)
    {

        // create a OptionalDouble
        OptionalDouble opdouble = OptionalDouble.of(0.23425);

        // apply ifPresent(DoubleConsumer)
        opdouble.ifPresent((value) -> {
            value = Math.pow(value, 4);
            System.out.println("Value after modification:=> "
                               + value);
        });
    }
}

Output: Program 2:

Java

// Java program to demonstrate
// OptionalDouble.ifPresent(DoubleConsumer) method

import java.util.OptionalDouble;

public class GFG {

    public static void main(String[] args)
    {

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

        // apply ifPresent(DoubleConsumer)
        opdouble.ifPresent((value) -> {
            System.out.println("Value:=> "
                               + value);
        });

        System.out.println("As OptionalDouble is empty value"
                           + " is not modified");
    }
}

Output: References: https://docs.oracle.com/javase/10/docs/api/java/util/OptionalDouble.html#ifPresent(java.util.function.DoubleConsumer)