Learn Java 8 Streams API[Practically]

Table of contents

• What is the streams API all about?
  • Intermediate operations
  • Terminal operations
  • Advantages

• When should it be used?

• Using Java 8 streams practically

• Java streams API learning Resources
• Summary

What is the streams API all about?

Streams bring functional programming to Java. The heavy use of lambda expressions gives it a JavaScript-like feeling.

IntStream
        .range(1, 10)
        .skip(5)
        .forEach(x -> System.out.println(x));/* Use of lambda expressions */

A stream pipeline consists of a source (such as a Collection, an array, a generator function, or an I/O channel); followed by zero or more intermediate operations such as Stream.filter or Stream.map; and a terminal operation such as Stream.forEach or Stream.reduce. - Oracle Docs

 

Stream operations are eitherintermediate or terminal.

Intermediate operations

Intermediate stream operations receive a Stream Input and returns Stream Output, so we can chain multiple intermediate operations.

The piece of code 👇🏾 returns a stream that can be passed to another intermediate or terminal operation

Stream.of(2, 1, 3)// Stream
      .sorted();// Intermediate operation

Terminal operations

Terminal stream operations receive a Stream Input and returns Non-stream Output or Void.

The piece of code 👇🏾 performs a terminal operation forEach() to print the stream values sorted by the intermediate operation sorted().

Stream.of(2, 1, 3)//Stream
      .sorted()//Intermediate operation
      .forEach(System.out::println);//Terminal operation

For more examples of using Java Streams, checkout JavaTpoint and this GitHub repo.

Advantages

• Simpler and cleaner code.
• Using Streams will make you a more efficient Java programmer
• Streams encourage looser coupling. Your stream-handling code doesn't need to know the source of the stream, or its eventual terminating method - Source

When should it be used?

Well, every time 😁... every time possible. Reading about streams, and its advantages you would want it throughout your code.

Now to what you've been waiting for; Practical scenarios.

Using Java 8 streams practically

Task 1

Checks from a list of airplanes if they all meet the criteria of a cargo plane

Using Streams

Below are chained stream operations

boolean areCargoPlanes = airplanes
        .stream()
        .filter(airplane -> airplane.getLoadCapacity() > 705)/*Hypothetical load of small planes */
        .filter(airplane -> airplane.getNumberOfSeats() < 5)
        .allMatch(airplane -> airplane.isCargo());

Without Streams

The code below is not an exact match of what the code with the Stream API does.

boolean areCargoPlanes = false;

for (String airplaneStr: airplanes) {
    if (airplane.getLoadCapacity() > 705) { //Hypothetical load of small planes
        if (airplane.getNumberOfSeats() < 5) {
            if (airplane.isCargo()) {
                areCargoPlanes = true;  
            }else {
                break;
            }
        }
    }
}

Task 2

From a list of guests in a hotel, print guests first and last name in alphabetical order.

Using Streams

List<RoomGuest> hotelGuests = new ArrayList<>();

hotelGuests.stream().sorted((o1, o2) -> {
    if (o1.getLastName().equals(o2.getLastName())) {
        return o1.getFirstName().compareToIgnoreCase(o2.getFirstName());
    }
    return o1.getLastName().compareTo(o2.getLastName());
}).forEach(System.out::println);

Without Streams

Just imagine the amount of code.

Resources

The best resource is Oracle's documentation on Java Stream API.

1. Java 8 STREAMS Tutorial on Youtube
2. The Java 8 Stream API Tutorial by Baeldung blog.
3. An In-Depth guide to Java 8 Stream API by Java2Blog
4. A Guide to Java Streams in Java 8: In-Depth Tutorial With Examples by Stackify blog.

Summary

In this post, we've learnt about Java 8 Streams and seen its benefits.

Knowledge of Java 8 streams is very essential and will come in handy as a beginner developer meeting a new codebase.

Thank you for reading. I mostly write tutorials on the problems I have faced and whatever new tech I explore, so stay tuned for the next article(I will be writing about files conversion).

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