The ifPresentOrElse method of the Optional class is an instance method that is used to perform an action based on whether or not the object’s value is present.
This method implements the Consumer interface and an implementation of the Runnable interface.
The accept method of the Consumer interface will be called when the value is present.
The value of the optional instance is passed as the parameter for the accept method.
The run method of the Runnable interface will be called with no parameters when the value is not present.
To learn what
Optionalclass is, refer to What is the optional class in Java?
Optional classThe Optional class is defined in the java.util package. Use the import statement below to import the Optional class.
import java.util.Optional;
public void ifPresentOrElse(Consumer<? super T> action, Runnable emptyAction)
Consumer<? super T> action: An implementation of the Consumer interface.
Runnable emptyAction: An implementation of the Runnable interface.
The ifPresentOrElse method doesn’t return anything.
In the code below, we create an instance of the Optional class using the method ofNullable for different values.
The implementation of the Consumer interface that prints the value stored in the Optional instance and the implementation of the Runnable interface that prints the string, No value in optional object is defined.
Refer to What is the optional class in Java? to learn more about the
ofNullablemethod.
In the first example, we create an Optional object from a non-empty string.
Hence, the accept() method of the Consumer interface implementation gets executed as the optional object has a value.
In the third example, we create an Optional object from a null value. Since the value passed is null, the method ofNullable replaces it with an empty Optional.
Hence, the run() method of the Runnable interface implementation is executed as the optional object has no value.
import java.util.Optional;import java.util.function.Consumer;class Main {public static void main(String[] args) {Consumer<String> stringConsumer = (s) -> System.out.println("The value stored in Optional object - " + s);Runnable runnable = () -> System.out.println("No value stored in the Optional object");String test = "hello-educative";Optional<String> stringOptional = Optional.ofNullable(test);System.out.println("When a value is present - ");stringOptional.ifPresentOrElse(stringConsumer, runnable);System.out.println("----------");test = null;System.out.println("When no value is present - ");stringOptional = Optional.ofNullable(test);stringOptional.ifPresentOrElse(stringConsumer, runnable);}}
When a value is present -
The value stored in Optional object - hello-educative
----------
When no value is present -
No value stored in the Optional object