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Java Academy · Lesson

Stream Sources

Discover where streams come from: collections, arrays, and generators.

Stream Sources is a free Java Academy lesson on CoddyKit — lesson 1 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Java Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Intro

Streams let you process data in pipelines. First step: know their sources.

Collections

You can call stream() on collections such as List, Set, or Queue.

Code: list stream

This turns a List into a Stream and prints each element.

import java.util.*;public class Main {
  public static void main(String[] args) {
    List<String> names = Arrays.asList("Ada", "Bob", "Eve");
    names.stream().forEach(System.out::println);
  }
}

Arrays

Arrays can be turned into streams using Arrays.stream(array).

Code: array stream

This converts an int array into an IntStream and prints values.

import java.util.*;import java.util.stream.*;public class Main {
  public static void main(String[] args) {
    int[] nums = {1, 2, 3};
    IntStream s = Arrays.stream(nums);
    s.forEach(System.out::println);
  }
}

Generated

You can generate infinite streams using Stream.generate or Stream.iterate.

Stream sources check

Quick check: Which is NOT a common source of a Java Stream?

Recap

Recap: Streams start from collections, arrays, or generators. Next you will learn map/filter/reduce.

Frequently asked questions

Is the “Stream Sources” lesson free?

Yes — the full text of “Stream Sources” is free to read here on the web, and the Java Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Java Academy course, upgrade to CoddyKit PRO.

What will I learn in “Stream Sources”?

Discover where streams come from: collections, arrays, and generators. You practise Java Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Java Academy?

No prior experience is required. Java Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 3, so you can start here or from the beginning and move at your own pace.

How long does the “Stream Sources” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Java Academy lesson?

Yes. Every Java Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Stream Sources
  2. map/filter/reduce
  3. Collectors & Grouping
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