The stream() method of java.util.Optional class in Java is used to get the sequential stream of the only value present in this Optional instance. If there is no value present in this Optional instance, then this method returns returns an empty Stream.
Syntax:
public Stream<T> stream()
Parameters: This method do not accept any parameter.
Return value: This method returns the sequential stream of the only value present in this Optional instance. If there is no value present in this Optional instance, then this method returns an empty Stream.
Below programs illustrate stream() method:
Note: Below programs require JDK 9 and above to execute.
Program 1:
// Java program to demonstrate// Optional.stream() method import java.util.*; public class GFG { public static void main(String[] args) { // create a Optional Optional<Integer> op = Optional.of(9455); // print value System.out.println("Optional: " + op); // get the Stream System.out.println("Getting the Stream:"); op.stream().forEach(System.out::println); }} |
Output:
Optional: Optional[9455] Getting the Stream: 9455
Program 2:
// Java program to demonstrate// Optional.stream() method import java.util.*; public class GFG { public static void main(String[] args) { // create a Optional Optional<Integer> op = Optional.empty(); // print value System.out.println("Optional: " + op); try { // get the Stream System.out.println("Getting the Stream:"); op.stream().forEach(System.out::println); } catch (Exception e) { System.out.println(e); } }} |
Output:
Optional: Optional.empty Getting the Stream:
Reference: https://docs.oracle.com/javase/9/docs/api/java/util/Optional.html#stream–
