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Module 1: Introduction to Threads

Learning Objectives

Understand the fundamentals of concurrent programming in Java
Create and manage threads using Java's Thread class
Identify common threading issues and synchronization challenges
Implement basic thread synchronization techniques
Apply multi-threading concepts to improve application performance
Explain why concurrency is more likely to help an I/O-bound application than a CPU-bound application
Explain thread lifecycle states (NEW, RUNNABLE, BLOCKED, WAITING, TERMINATED) and their transitions
Examine whether a described scenario is taking advantage of concurrency
Examine whether running a given code snippet has the potential to suffer from a race condition
Design and implement a class that implements Runnable to execute functionality concurrently

Introduction to Threading

Threads allow Java applications to perform multiple operations concurrently. A thread is a lightweight process that can execute independently while sharing the same resources as other threads within a process.

In this module, we'll explore how to create and use threads in Java, understand thread lifecycle, and learn about common challenges in concurrent programming.

When developing programs, you always start with one execution path (the main method). However, as applications become more complex, using a single thread can create bottlenecks. Multithreading allows you to create additional execution paths that run concurrently, improving performance particularly for I/O-bound operations.

Creating Threads in Java

There are two primary ways to create threads in Java:

// Method 1: Extending Thread class
public class MyThread extends Thread {
    public void run() {
        System.out.println("Thread is running");
    }
}

// Usage
MyThread thread = new MyThread();
thread.start();

// Method 2: Implementing Runnable interface
public class MyRunnable implements Runnable {
    public void run() {
        System.out.println("Thread is running");
    }
}

// Usage
Thread thread = new Thread(new MyRunnable());
thread.start();

Remember to always call start() rather than run() directly. Calling start() creates a new thread that executes the run() method, while calling run() directly just executes the method in the current thread.

Thread Lifecycle States

NEW: Thread exists but hasn't been started yet
RUNNABLE: Thread is actively running or ready to run
BLOCKED: Thread is waiting to acquire a lock
WAITING: Thread is waiting indefinitely for another thread to perform an action
TERMINATED: Thread has completed execution or been stopped

You can check a thread's state using thread.getState() method.

Key Topics

Thread Basics

Learn about the fundamentals of Java threads.

Thread lifecycle
Creating threads
Thread vs. Runnable

Thread Management

Understand how to control thread execution.

Starting and stopping threads
Thread priority
Thread joining

Synchronization

Learn about thread safety and coordination.

Synchronized methods
Synchronized blocks
Race conditions

Common Challenges

Identify and solve threading issues.

Deadlocks
Thread starvation
Thread safety strategies

Resources

Intro to Threads Code-Along Starter

Starter code for implementing thread concepts.

View Repository

Intro to Threads Code-Along Solution

Solution code for the threading implementation.

View Repository

Hacking Passwords Project

A practical project demonstrating threading concepts.

View Repository

Code-Alongs

Additional code-along exercises for this sprint.

View Code-Alongs

Sprint Challenge

Access the sprint challenge for this unit.

View Challenge