java-tutorial

15) Concurrency: Threads, Executors, Futures

Goal

Understand how to run tasks concurrently and how to avoid common mistakes.

Thread basics

var t = new Thread(() -> System.out.println("running"));
t.start();

Prefer executors

ExecutorService pool = Executors.newFixedThreadPool(4);
Future<Integer> result = pool.submit(() -> 40 + 2);
System.out.println(result.get());
pool.shutdown();

Common hazards

Exercises

  1. Run 10 tasks in a fixed thread pool and collect results.
  2. Implement a thread-safe counter using AtomicInteger.
  3. Demonstrate a race condition, then fix it.

Table of contents

  1. Getting Started: Install, run, and your first program
  2. Java Basics: types, variables, operators, formatting
  3. Control Flow: if/switch/loops
  4. Methods: parameters, return values, overloading
  5. OOP: classes, objects, encapsulation
  6. Inheritance & Polymorphism (and when not to use them)
  7. Interfaces, abstract classes, and design basics
  8. Exceptions and error handling
  9. Strings, files, and I/O basics
  10. Collections: List/Set/Map and Big-O intuition
  11. Generics (the useful parts)
  12. Lambdas & Streams
  13. Dates and time (java.time)
  14. Testing with JUnit 5 (basics)
  15. Concurrency: threads, executors, futures
  16. JVM basics: memory, GC, performance habits
  17. Build tools: Maven essentials (recommended)
  18. Next steps: projects to build