The
or() method of
java.util.Optional class in Java is used to get this Optional instance if any value is present. If there is no value present in this Optional instance, then this method returns an Optional instance with the value generated from the specified supplier.
Syntax:
public Optional<T> or(Supplier<T> supplier)
Parameters: This method accepts
supplier as a parameter of type T to generate an Optional instance with the value generated from the specified supplier.
Return supplier: This method returns this
Optional instance, if any value is present. If there is no value present in this Optional instance, then this method returns an Optional instance with the value generated from the specified supplier.
Exception: This method throws NullPointerException if the supplying function is null or produces a null result.
Below programs illustrate or() method:
Note: As this method was added in Java 9, the programs need JDK 9 to execute.
Program 1:
Output:
Optional: Optional[9455]
Optional by or(() -> Optional.of(100)) method: Optional[9455]
Program 2:
