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) methodimport 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) methodimport 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)
