in this article, we will learn to use the ofnullable() method of stream in java 9. we will first go through the stream class, after that we will learn about the ofnullable() method along with its syntax and real-world use cases.

stream class

stream was introduced in java 8, the stream api is used to process collections of objects. it represents a sequence of elements that support various operations to perform computations in parallel.

creating an instance of a stream:

stream<t> stream;

a stream is not a type of data structure, it takes input from collections, arrays, etc.

the ofnullable() method

the ofnullable() method is a static method of the stream class that returns a sequential stream containing a single element if non-null, otherwise returns an empty.

this method does not throw any exceptions. java 9 has introduced this method to avoid nullpointerexceptions and also avoid null checks of streams.

the main objective of using the ofnullable() method is to return an empty option if the value is null.

syntax

the following is the syntax of the ofnullable() method declaration:

static <t> stream<t> ofnullable(t t)

this method accepts a single parameter "t", which is the single element of which the stream is to be returned.

when to use the ofnullable() method?

the following are the two real-world use cases of the ofnullable() method in java:

processing database results:

in the real-world applications, the stream.ofnullable() method converts the nullable database entries to a stream of valid entities.

list<customer> customers = customerids.stream()
                                   .flatmap(id -> stream.ofnullable(database.findcustomer(id)))
                                   .collect(collectors.tolist());

configuration handling:

in the real-world applications, the stream.ofnullable() method can be used to process configuration settings and handle them properly.

config.foreach((key, value) -> {
            stream.ofnullable(value)
                  .map(v -> key + "=" + v)
                  .foreach(system.out::println);
        });

examples of ofnullable() method

example 1

below is an example of the ofnullable() method for counting elements in a nullable stream:

import java.util.stream.stream;
public class ofnullablemethodtest1 {
   public static void main(string args[]) {
      system.out.println("tutorialspoint");
      int count = (int) stream.ofnullable(5000).count();
      system.out.println(count);
      system.out.println("tutorix");
      count = (int) stream.ofnullable(null).count();
      system.out.println(count);
   }
}

output

tutorialspoint
1
tutorix
0

example 2

below is an example of the ofnullable() method for printing null values and non-null values:

import java.util.stream.stream;
public class ofnullablemethodtest2 {
   public static void main(string args[]) {
      string str = null;
      stream.ofnullable(str).foreach(system.out::println); // prints nothing in the console
      str = "tutorialspoint";
      stream.ofnullable(str).foreach(system.out::println); // prints tutorialspoint
   }
}

output

tutorialspoint

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