LESSON 19

3.1 Lesson Outcomes

After completing this lesson, learners will be able to:

• Define threads and multithreading in Java.
• Explain the purpose of concurrency in Java applications.
• Create and run threads in Java.
• Differentiate between single-threaded and multithreaded applications.
• Explain the importance of multithreading in software development.

3.2 Overview

Modern software applications often perform multiple tasks simultaneously. Java supports multithreading, which allows applications to execute multiple threads concurrently to improve efficiency, responsiveness, and performance.

This lesson introduces learners to threads and concurrency in Java and explains how multithreading supports background processing and concurrent task execution. Learners will also explore how threads are created and managed in Java applications.

Multithreading is commonly used in:

• banking systems,
• gaming applications,
• web applications,
• mobile applications,
• and enterprise software.

Understanding multithreading is important because many modern software systems rely on concurrent processing.

KT1901 — Introduction to Threads

A thread is a lightweight unit of execution inside a Java program.

Threads allow applications to perform multiple tasks concurrently.

A Java application may contain:

• one thread,
• or multiple threads.

Importance of Threads

Threads help applications:

• improve performance,
• support multitasking,
• increase responsiveness,
• and process tasks concurrently.

KT1902 — Single-Threaded vs Multithreaded Applications

A single-threaded application executes one task at a time.

A multithreaded application executes multiple tasks concurrently.

Comparison

Importance of Multithreading

Multithreading improves:

• user experience,
• processing efficiency,
• and application performance.

KT1903 — Creating Threads Using the Thread Class

Threads can be created by extending the Thread class.

Example

class MyThread extends Thread {

    public void run() {

        System.out.println("Thread is running");
    }
}

Running the Thread

public class Main {

    public static void main(String[] args) {

        MyThread thread = new MyThread();

        thread.start();
    }
}

Output

Thread is running

Explanation

Importance of the Thread Class

The Thread class supports:

• concurrent processing,
• multitasking,
• and background operations.

KT1904 — Creating Threads Using Runnable Interface

Java also supports thread creation using the Runnable interface.

Example

class MyTask implements Runnable {

    public void run() {

        System.out.println("Runnable thread executing");
    }
}

Running the Runnable Thread

public class Main {

    public static void main(String[] args) {

        MyTask task = new MyTask();

        Thread thread = new Thread(task);

        thread.start();
    }
}

Output

Runnable thread executing

Importance of Runnable

Runnable:

• supports flexible thread design,
• allows class inheritance elsewhere,
• and is widely used in Java development.

KT1905 — Thread Lifecycle

Threads move through different states during execution.

Thread States

Importance of Thread Lifecycle

Understanding thread states helps developers:

• manage execution,
• improve performance,
• and avoid application issues.

KT1906 — Thread Sleep

The sleep() method pauses thread execution temporarily.

Example

public class Main {

    public static void main(String[] args)
            throws InterruptedException {

        System.out.println("Start");

        Thread.sleep(2000);

        System.out.println("End");
    }
}

Output

Start
End

Explanation

2000 milliseconds = 2 seconds

The thread pauses execution for 2 seconds.

Importance of sleep()

The sleep() method helps:

• manage timing,
• delay execution,
• and control thread scheduling.

KT1907 — Concurrency in Java Applications

Concurrency allows multiple tasks to progress during the same execution period.

Concurrency improves:

• responsiveness,
• multitasking,
• and application efficiency.

Examples of Concurrency

Concurrency is used in:

• downloading files while browsing,
• video streaming,
• background notifications,
• and transaction processing.

KT1908 — Challenges of Multithreading

Multithreading may introduce:

• synchronization issues,
• resource conflicts,
• and complexity.

Common Challenges

Importance of Thread Management

Proper thread management helps:

• maintain stability,
• improve performance,
• and prevent application errors.

KT1909 — Real-World Use of Multithreading

Multithreading is used in:

• banking systems,
• gaming applications,
• mobile applications,
• web servers,
• and enterprise systems.

Examples:

• background processing,
• simultaneous user handling,
• transaction processing,
• and live system monitoring.

Multithreading improves efficiency and responsiveness in software applications.

3.5 Key Notes / Summary

• Threads are lightweight units of execution.
• Multithreading supports concurrent processing.
• Java supports Thread and Runnable approaches.
• The run() method contains thread tasks.
• The start() method begins execution.
• Threads move through lifecycle states.
• Multithreading improves application performance and responsiveness.