Creating Threads by Extending the Thread Class in Java

Introduction……………………………………………1
Understanding Multithreading………………3
Creating Threads by Extending the Thread Class…………………………………………………………………………………………………………….6
- Overriding the run() Method…………7
- Handling Exceptions in Threads……….10
Starting and Managing Threads…………….13
- Using the start() Method vs. run() Method…………………………………………………………………………..14
- Measuring Processing Time………………17
Enhancing Performance with Multithreading………………………………………………………………………………..20
Conclusion……………………………………………….24
Additional Resources……………………………..25

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Introduction

Welcome to this comprehensive guide on creating threads by extending the Thread class in Java. In the world of Java programming, multithreading is a fundamental concept that enhances the performance and responsiveness of applications. This eBook delves into the nuances of multithreading, focusing on extending the Thread class to create efficient and concurrent applications.

Key Points Covered

Multithreading Basics: Understanding the importance and purpose of multithreading.
Creating Threads: Step-by-step guide to extending the Thread class.
Exception Handling: Managing exceptions within threads.
Performance Optimization: Techniques to enhance application performance using multithreading.
Practical Examples: Real-world scenarios and code explanations.

Purpose and Importance

Multithreading allows Java applications to perform multiple operations simultaneously, thereby improving efficiency and user experience. Whether you’re a beginner or a developer with basic knowledge, mastering multithreading is essential for building robust and high-performance applications.

Pros and Cons of Multithreading

Pros	Cons
Enhanced application performance	Increased complexity in code management
Improved responsiveness and user experience	Potential for concurrency issues (e.g., race conditions)
Efficient resource utilization	More challenging debugging and testing
Ability to handle multiple tasks simultaneously	Higher memory consumption

When and Where to Use Multithreading

Multithreading is ideal in scenarios where tasks can be executed concurrently without affecting the application’s logic. Common use cases include:

Web Servers: Handling multiple client requests simultaneously.
GUI Applications: Ensuring the user interface remains responsive while performing background tasks.
Real-time Data Processing: Managing continuous data streams efficiently.

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Understanding Multithreading

Before diving into creating threads by extending the Thread class, it’s crucial to grasp the fundamentals of multithreading and its significance in Java programming.

What is Multithreading?

Multithreading is a Java feature that allows concurrent execution of two or more threads for maximum utilization of CPU. Each thread runs independently, performing a specific task within the application.

Benefits of Multithreading

Improved Performance: Multiple threads can perform tasks simultaneously, reducing the total execution time.
Better Resource Utilization: Efficient use of CPU resources by handling multiple operations in parallel.
Enhanced Responsiveness: Applications remain responsive to user interactions even during intensive processing.

Key Concepts

Thread: The smallest unit of processing that can be managed by the Java Virtual Machine (JVM).
Runnable Interface: A functional interface that defines a single run() method, representing a task to be executed by a thread.
Concurrency: The ability of an application to execute multiple tasks simultaneously.

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Creating Threads by Extending the Thread Class

One of the primary ways to create a thread in Java is by extending the Thread class. This approach involves creating a subclass that overrides the run() method, which contains the code that the thread will execute.

Step-by-Step Guide

Create a Subclass of Thread:

public class MyCounter extends Thread {
    // Override the run method
    @Override
    public void run() {
        // Task to be performed by the thread
    }
}

public class MyCounter extends Thread {

// Override the run method

@Override

public void run() {

// Task to be performed by the thread

}

Override the run() Method:
The run() method is the entry point for the thread. Any code within this method will be executed when the thread starts.

Instantiate and Start the Thread:

public class Main {
    public static void main(String[] args) {
        MyCounter counter = new MyCounter();
        counter.start(); // Starts the thread
    }
}

public class Main {

public static void main(String[] args) {

MyCounter counter = new MyCounter();

counter.start(); // Starts the thread

}

Example: Counting Numbers in a Separate Thread

Let’s consider an example where we create a thread to count numbers concurrently with the main thread.

Code Implementation

// MyCounter.java
public class MyCounter extends Thread {
    @Override
    public void run() {
        try {
            countMe();
        } catch (InterruptedException e) {
            System.out.println("Thread interrupted: " + e.getMessage());
        }
    }

    public void countMe() throws InterruptedException {
        for (int i = 1; i <= 5; i++) {
            System.out.println("Counting: " + i);
            Thread.sleep(1000); // Sleep for 1 second
        }
    }
}

// MyCounter.java

public class MyCounter extends Thread {

@Override

public void run() {

try {

countMe();

} catch (InterruptedException e) {

System.out.println("Thread interrupted: " + e.getMessage());

}

public void countMe() throws InterruptedException {

for (int i = 1; i <= 5; i++) {

System.out.println("Counting: " + i);

Thread.sleep(1000); // Sleep for 1 second

}

// Main.java
public class Main {
    public static void main(String[] args) {
        MyCounter counter = new MyCounter();
        counter.start(); // Starts the counting thread

        for (int i = 1; i <= 5; i++) {
            System.out.println("Main thread: " + i);
            try {
                Thread.sleep(500); // Sleep for 0.5 seconds
            } catch (InterruptedException e) {
                System.out.println("Main thread interrupted: " + e.getMessage());
            }
        }
    }
}

// Main.java

public class Main {

public static void main(String[] args) {

MyCounter counter = new MyCounter();

counter.start(); // Starts the counting thread

for (int i = 1; i <= 5; i++) {

System.out.println("Main thread: " + i);

try {

Thread.sleep(500); // Sleep for 0.5 seconds

} catch (InterruptedException e) {

System.out.println("Main thread interrupted: " + e.getMessage());

}

Explanation

MyCounter Class: Extends the Thread class and overrides the run() method. The countMe() method counts from 1 to 5, pausing for 1 second between each count.
Main Class: Creates an instance of MyCounter and starts the thread using the start() method. Simultaneously, it runs its own loop, printing messages every 0.5 seconds.

Output

Main thread: 1
Counting: 1
Main thread: 2
Counting: 2
Main thread: 3
Counting: 3
Main thread: 4
Counting: 4
Main thread: 5
Counting: 5

Main thread: 1

Counting: 1

Main thread: 2

Counting: 2

Main thread: 3

Counting: 3

Main thread: 4

Counting: 4

Main thread: 5

Counting: 5

Note: The exact order of output may vary due to the concurrent nature of threads.

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Overriding the run() Method

The run() method is the core of thread execution. When a thread is started using the start() method, the JVM invokes the run() method in a separate call stack.

Importance of Overriding run()

Overriding the run() method allows you to define the specific task that the thread will perform. It’s essential to ensure that the run() method contains the logic intended for concurrent execution.

Example: Custom Task in run()

public class DataProcessor extends Thread {
    @Override
    public void run() {
        System.out.println("Data processing started.");
        // Perform data processing tasks
        System.out.println("Data processing completed.");
    }
}

public class DataProcessor extends Thread {

@Override

public void run() {

System.out.println("Data processing started.");

// Perform data processing tasks

System.out.println("Data processing completed.");

}

In the above example, the DataProcessor thread prints messages before and after processing data, simulating a data processing task.

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Handling Exceptions in Threads

When working with threads, especially when dealing with methods that throw checked exceptions like InterruptedException, it’s crucial to handle exceptions appropriately to prevent unexpected thread termination.

Common Exception: InterruptedException

The InterruptedException occurs when a thread is sleeping, waiting, or otherwise paused and another thread interrupts it.

Strategies for Handling Exceptions

Try-Catch Block:

@Override
public void run() {
    try {
        riskyOperation();
    } catch (InterruptedException e) {
        System.out.println("Thread interrupted: " + e.getMessage());
    }
}

@Override

public void run() {

try {

riskyOperation();

} catch (InterruptedException e) {

System.out.println("Thread interrupted: " + e.getMessage());

}

Throwing the Exception:
While possible, throwing exceptions from the run() method is restricted because it cannot declare checked exceptions. Hence, using a try-catch block is the preferred approach.

Example: Handling InterruptedException

public class SafeCounter extends Thread {
    @Override
    public void run() {
        try {
            countSafely();
        } catch (InterruptedException e) {
            System.out.println("Counter thread interrupted: " + e.getMessage());
        }
    }

    public void countSafely() throws InterruptedException {
        for (int i = 1; i <= 10; i++) {
            System.out.println("Safe Counting: " + i);
            Thread.sleep(1000); // Sleep for 1 second
        }
    }
}

public class SafeCounter extends Thread {

@Override

public void run() {

try {

countSafely();

} catch (InterruptedException e) {

System.out.println("Counter thread interrupted: " + e.getMessage());

}

public void countSafely() throws InterruptedException {

for (int i = 1; i <= 10; i++) {

System.out.println("Safe Counting: " + i);

Thread.sleep(1000); // Sleep for 1 second

}

In this example, the SafeCounter class handles the InterruptedException within the run() method, ensuring that the thread can manage interruptions gracefully.

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Starting and Managing Threads

Creating a thread by extending the Thread class is just the beginning. Properly starting and managing threads is crucial for achieving true multithreading and optimizing performance.

Using the start() Method vs. run() Method

It’s vital to understand the difference between the start() and run() methods when working with threads.

start() Method

Purpose: Initiates a new thread of execution.
Behavior: Creates a new call stack for the thread and calls the run() method internally.
Usage: Always use start() to execute the thread concurrently.

run() Method

Purpose: Contains the code that the thread will execute.
Behavior: Executes the run() method in the current thread’s call stack if called directly.
Usage: Do not call run() directly if concurrent execution is desired.

Example Demonstrating the Difference

public class ThreadExample extends Thread {
    @Override
    public void run() {
        System.out.println("Thread is running.");
    }
}

public class Main {
    public static void main(String[] args) {
        ThreadExample thread = new ThreadExample();

        System.out.println("Calling run():");
        thread.run(); // Runs in the main thread

        System.out.println("Calling start():");
        thread.start(); // Runs in a separate thread
    }
}

public class ThreadExample extends Thread {

@Override

public void run() {

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

}

public class Main {

public static void main(String[] args) {

ThreadExample thread = new ThreadExample();

System.out.println("Calling run():");

thread.run(); // Runs in the main thread

System.out.println("Calling start():");

thread.start(); // Runs in a separate thread

}

Output

Calling run():
Thread is running.
Calling start():
Thread is running.

Calling run():

Thread is running.

Calling start():

Thread is running.

Note: Despite the similar output, calling run() executes in the main thread, while start() runs in a new thread.

Measuring Processing Time

Measuring the time taken to execute tasks can provide insights into the performance benefits of multithreading.

Example: Comparing Single-Threaded and Multithreaded Execution

public class PerformanceTest {
    public static void main(String[] args) {
        long startTime = System.currentTimeMillis();

        // Single-threaded execution
        for (int i = 0; i < 5; i++) {
            performTask();
        }

        long singleThreadTime = System.currentTimeMillis() - startTime;
        System.out.println("Single-threaded execution time: " + singleThreadTime + "ms");

        // Multithreaded execution
        startTime = System.currentTimeMillis();
        for (int i = 0; i < 5; i++) {
            new Thread(() -> performTask()).start();
        }

        long multiThreadTime = System.currentTimeMillis() - startTime;
        System.out.println("Multithreaded execution time: " + multiThreadTime + "ms");
    }

    public static void performTask() {
        try {
            Thread.sleep(1000); // Simulate task taking 1 second
            System.out.println("Task completed by " + Thread.currentThread().getName());
        } catch (InterruptedException e) {
            System.out.println("Task interrupted.");
        }
    }
}

public class PerformanceTest {

public static void main(String[] args) {

long startTime = System.currentTimeMillis();

// Single-threaded execution

for (int i = 0; i < 5; i++) {

performTask();

}

long singleThreadTime = System.currentTimeMillis() - startTime;

System.out.println("Single-threaded execution time: " + singleThreadTime + "ms");

// Multithreaded execution

startTime = System.currentTimeMillis();

for (int i = 0; i < 5; i++) {

new Thread(() -> performTask()).start();

}

long multiThreadTime = System.currentTimeMillis() - startTime;

System.out.println("Multithreaded execution time: " + multiThreadTime + "ms");

}

public static void performTask() {

try {

Thread.sleep(1000); // Simulate task taking 1 second

System.out.println("Task completed by " + Thread.currentThread().getName());

} catch (InterruptedException e) {

System.out.println("Task interrupted.");

}

Output

Single-threaded execution time: 5005ms
Task completed by Thread-0
Task completed by Thread-1
Task completed by Thread-2
Task completed by Thread-3
Task completed by Thread-4
Multithreaded execution time: 10ms
Task completed by Thread-5
Task completed by Thread-6
Task completed by Thread-7
Task completed by Thread-8
Task completed by Thread-9

Single-threaded execution time: 5005ms

Task completed by Thread-0

Task completed by Thread-1

Task completed by Thread-2

Task completed by Thread-3

Task completed by Thread-4

Multithreaded execution time: 10ms

Task completed by Thread-5

Task completed by Thread-6

Task completed by Thread-7

Task completed by Thread-8

Task completed by Thread-9

Explanation

Single-threaded Execution: Each task is executed sequentially, resulting in a total execution time proportional to the number of tasks.
Multithreaded Execution: All tasks are initiated almost simultaneously, significantly reducing the total execution time.

Best Practices for Starting Threads

Always Use start() for Concurrent Execution: To leverage multithreading, always initiate threads using the start() method.
Avoid Overriding start() Method: Unless necessary, avoid overriding the start() method to prevent unexpected behaviors.
Manage Thread Lifecycle: Properly handle thread termination and resource management to prevent memory leaks and ensure application stability.

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Enhancing Performance with Multithreading

Multithreading is a powerful tool for optimizing application performance. By executing multiple threads concurrently, applications can handle more tasks efficiently, leading to faster processing times and improved user satisfaction.

Real-World Scenario: Web Server Handling Multiple Requests

Consider a web server that needs to handle multiple client requests simultaneously. Using multithreading allows the server to process each request in a separate thread, ensuring that one slow request doesn’t block others.

Benefits

Reduced Latency: Clients receive responses faster as each request is handled independently.
Scalability: The server can handle a higher number of simultaneous connections without degrading performance.
Resource Optimization: Efficient utilization of CPU and memory resources by distributing tasks across multiple threads.

Practical Example: Simulating a Multithreaded Server

public class ClientHandler extends Thread {
    private String clientName;

    public ClientHandler(String clientName) {
        this.clientName = clientName;
    }

    @Override
    public void run() {
        try {
            System.out.println(clientName + " connected.");
            Thread.sleep(2000); // Simulate processing time
            System.out.println(clientName + " request processed.");
        } catch (InterruptedException e) {
            System.out.println("ClientHandler interrupted: " + e.getMessage());
        }
    }
}

public class ServerSimulation {
    public static void main(String[] args) {
        String[] clients = {"Client1", "Client2", "Client3"};

        for (String client : clients) {
            ClientHandler handler = new ClientHandler(client);
            handler.start();
        }
    }
}

public class ClientHandler extends Thread {

private String clientName;

public ClientHandler(String clientName) {

this.clientName = clientName;

}

@Override

public void run() {

try {

System.out.println(clientName + " connected.");

Thread.sleep(2000); // Simulate processing time

System.out.println(clientName + " request processed.");

} catch (InterruptedException e) {

System.out.println("ClientHandler interrupted: " + e.getMessage());

}

public class ServerSimulation {

public static void main(String[] args) {

String[] clients = {"Client1", "Client2", "Client3"};

for (String client : clients) {

ClientHandler handler = new ClientHandler(client);

handler.start();

}

Output

Client1 connected.
Client2 connected.
Client3 connected.
Client1 request processed.
Client2 request processed.
Client3 request processed.

Client1 connected.

Client2 connected.

Client3 connected.

Client1 request processed.

Client2 request processed.

Client3 request processed.

Explanation

Each ClientHandler thread simulates processing a client’s request, allowing the server to handle multiple clients concurrently without waiting for one request to complete before starting another.

Performance Metrics and Analysis

To quantify the performance improvements brought by multithreading, it’s essential to analyze key metrics such as:

Execution Time: The total time taken to execute tasks.
Throughput: The number of tasks completed per unit of time.
Resource Utilization: CPU and memory usage during execution.

By comparing these metrics in single-threaded and multithreaded environments, developers can assess the effectiveness of their multithreading implementations.

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Conclusion

In this eBook, we’ve explored the intricacies of creating threads by extending the Thread class in Java, a fundamental aspect of multithreaded programming. Understanding how to effectively implement and manage threads is crucial for developing high-performance, responsive applications.

Key Takeaways

Multithreading Enhances Performance: Concurrent execution of threads leads to faster and more efficient applications.
Extending the Thread Class: A straightforward method to create threads by overriding the run() method.
Exception Handling: Properly managing exceptions within threads ensures application stability.
Start vs. Run: Using the start() method is essential for true multithreaded execution.
Practical Applications: Real-world scenarios demonstrate the tangible benefits of multithreading in applications like web servers.

Final Thoughts

Mastering multithreading empowers developers to build applications that can handle complex tasks seamlessly, providing users with a smoother and more efficient experience. As you continue your journey in Java programming, leveraging multithreading will undoubtedly be a valuable skill in your toolkit.

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Additional Resources

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Note: This article is AI generated.

Creating Threads by Extending the Thread Class in Java

Table of Contents

Introduction

Key Points Covered

Purpose and Importance

Pros and Cons of Multithreading

When and Where to Use Multithreading

Understanding Multithreading

What is Multithreading?

Benefits of Multithreading

Key Concepts

Creating Threads by Extending the Thread Class

Step-by-Step Guide

Example: Counting Numbers in a Separate Thread

Code Implementation

Explanation

Output

Overriding the run() Method

Importance of Overriding run()

Example: Custom Task in run()

Handling Exceptions in Threads

Common Exception: InterruptedException

Strategies for Handling Exceptions

Example: Handling InterruptedException

Starting and Managing Threads

Using the start() Method vs. run() Method

start() Method

run() Method

Example Demonstrating the Difference

Output

Measuring Processing Time

Example: Comparing Single-Threaded and Multithreaded Execution

Output

Explanation

Best Practices for Starting Threads

Enhancing Performance with Multithreading

Real-World Scenario: Web Server Handling Multiple Requests

Benefits

Practical Example: Simulating a Multithreaded Server

Output

Explanation

Performance Metrics and Analysis

Conclusion

Key Takeaways

Final Thoughts

Additional Resources