14.3 - Creating Threads in Java
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Creating Threads Using the Thread Class
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Today we're going to learn how to create threads in Java using the Thread class. When you extend the Thread class, you only need to override the `run()` method to define what the thread will do. Can anyone explain what the `run()` method is?
The `run()` method contains the code that will execute when the thread starts.
Exactly! Let’s see a basic example. In this code, we create a class called MyThread that extends Thread, and inside it, we override the `run()` method to print a message. What happens when we call `t1.start()`?
It starts a new thread and calls the `run()` method in that thread.
Good job! And remember, we never call the `run()` method directly; we always use `start()`. Now, can anyone remember how to instantiate and start the thread using this class?
We create an object of MyThread and then call `start()` on that object.
Perfect! To summarize, we use the Thread class by overriding `run()`, creating an instance, and starting it with `start()`.
Creating Threads Using the Runnable Interface
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Next, let’s explore how to create threads using the Runnable interface. This method lets us implement the `run()` method in a separate class. Why might we want to use this approach?
It allows us to separate the thread's behavior from the execution. Plus, we can implement other interfaces too.
Exactly! Good thinking! For instance, we can create a class MyRunnable that implements Runnable. When we create a thread, we pass an instance of MyRunnable as an argument. What command do we use to start this thread?
We still call `start()` on the Thread object, right?
"That's correct! Let’s see the example:
Introduction & Overview
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Quick Overview
Standard
In this section, we explore two primary methods of creating threads in Java: by extending the Thread class and implementing the Runnable interface. Each approach is demonstrated with code examples, highlighting their functionalities and use cases in concurrent programming.
Detailed
Creating Threads in Java
In Java, threads can be efficiently created using two main approaches: extending the Thread class and implementing the Runnable interface. Understanding these methods is crucial for managing multitasking in applications and ensuring optimal performance.
Using the Thread Class
To create a thread by extending the Thread class, you define a subclass that overrides the run() method to specify the task that the thread will execute. For example:
In this example, when t1.start() is invoked, the run() method is executed in a new thread, which prints "Thread is running".
Using the Runnable Interface
Alternatively, threads can be created by implementing the Runnable interface. This approach is beneficial for separating the thread's task from its execution. The code for this method looks like this:
Here, a thread is created by passing an instance of a class that implements Runnable to the Thread constructor. When t2.start() is called, it executes the run() method of MyRunnable. This method is particularly useful for passing parameters and improving code organization.
Overall, recognizing these two methods equips developers with flexibility in choosing how to implement threading, enhancing their ability to create responsive applications.
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Creating a Thread Using the Thread Class
Chapter 1 of 2
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Chapter Content
class MyThread extends Thread {
public void run() {
System.out.println("Thread is running");
}
}
MyThread t1 = new MyThread();
t1.start();
Detailed Explanation
In this chunk, we learn how to create a thread in Java by extending the Thread class. First, we define a new class called MyThread that inherits from Thread. Inside this class, we override the run() method, which contains the code that will be executed when the thread starts. After defining the MyThread class, we create an instance of it (t1), and then we call t1.start(). This call triggers the thread to begin executing, and it runs the code inside the run() method, printing "Thread is running" to the console.
Examples & Analogies
Think of creating a thread using the Thread class like scheduling a task for a worker in a factory. You give the worker (the thread) a specific task to perform (the code inside run()). When you call start(), it's like telling the worker to begin their job. They will get to work and complete the task independently, allowing you to manage other tasks simultaneously.
Creating a Thread Using the Runnable Interface
Chapter 2 of 2
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Chapter Content
class MyRunnable implements Runnable {
public void run() {
System.out.println("Runnable thread is running");
}
}
Thread t2 = new Thread(new MyRunnable());
t2.start();
Detailed Explanation
In this section, we create a thread by implementing the Runnable interface instead of extending the Thread class. We define a class MyRunnable that implements Runnable, overriding the run() method to specify what the thread should execute. When creating the new thread (t2), we pass an instance of MyRunnable to the Thread constructor. Finally, calling t2.start() begins the execution of the thread, which runs the code in the run() method, printing "Runnable thread is running".
Examples & Analogies
Using the Runnable interface can be compared to having a blueprint for a house. You can have multiple builders (threads) following the same blueprint (class implementing Runnable) to construct different houses (instances of threads). Each builder starts working when you say start(), leading to different houses being built simultaneously, demonstrating concurrent work.
Key Concepts
-
Creating Threads: Threads can be created in Java by extending the Thread class or implementing the Runnable interface.
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Thread Class: A straightforward method to create threads that involves subclassing Thread and overriding the run() method.
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Runnable Interface: This approach allows threads to be created without needing to extend the Thread class, promoting better code organization.
Examples & Applications
Example of creating a thread by extending the Thread class where MyThread overrides the run() method to print a message.
Example of creating a thread using the Runnable interface, allowing for cleaner code and enabling the class to implement multiple interfaces.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
Thread class starts with a run, it’s where the thread gets its fun!
Stories
Picture a busy factory where workers (threads) can either work on their own machines (Thread class) or come together for a project (Runnable interface). Each worker knows exactly what to do when their machine starts running!
Memory Tools
Remember 'TR' for Thread class and Runnable interface—T for Thread and R for Runnable, which makes creating threads straightforward!
Acronyms
Use 'TRI' to recall
= Thread
= Runnable
= Implementation lead to thread creation!
Flash Cards
Glossary
- Thread Class
A class in Java that is used to create threads by extending it and overriding the run() method.
- Runnable Interface
An interface that must be implemented when a class is intended to be executed by a thread.
- run() Method
The method that contains the code to be executed by the thread.
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