Introduction to Threads and Concurrency

Concurrency is an important concept in programming as it allows programs to execute multiple tasks simultaneously.
Concurrent programming in Java is achieved through the use of threads.
Threads are lightweight processes that can run independently of each other within a single program.

In this chapter, we will introduce the concept of threads and concurrent programming in Java.

Why Concurrent Programming is Important

Concurrent programming is important because it allows programs to execute multiple tasks at the same time, which can improve performance and make better use of system resources.

For example, a program that performs multiple network requests can execute these requests simultaneously using threads, reducing the overall time required to complete the requests.

Enabling Concurrent Programming in Java

Java provides built-in support for concurrent programming through its Thread class and Runnable interface. The Thread class provides methods to create and manage threads, while the Runnable interface defines the code to be executed in a separate thread.

Here's an example of creating a thread using the Thread class.

Main


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class MyThread extends Thread {
    public void run() {
        // Code to be executed in this thread
    }
}

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

In this example, we define a MyThread class that extends the Thread class and overrides the run method. We then create an instance of MyThread and start it by calling the start method. The run() method is executed in a separate thread.

Alternatively, we can create a thread using the Runnable interface.

Main


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class MyRunnable implements Runnable {
    public void run() {
        // Code to be executed in this thread
    }
}

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

Here, we define a MyRunnable class that implements the Runnable interface and overrides the run() method. We then create a Thread instance, passing MyRunnable as a constructor argument, and start the thread by calling the start() method.

Major Classes and Methods

Java provides several classes and methods to create and manage threads.

Here are some of the major ones:

Thread: The main class used to create and manage threads in Java.
Runnable: The interface used to define the code to be executed in a separate thread.
start(): The method used to start a thread.
sleep(): The method used to pause the execution of a thread for a specified amount of time.
join(): The method used to wait for a thread to complete its execution.
yield(): The method used to give up the CPU to another thread.

Synchronization

When multiple threads access shared resources, synchronization is needed to avoid conflicts and ensure data consistency. In Java, synchronization can be achieved using locks. A lock is an object that can be acquired by a thread, preventing other threads from accessing the same shared resource.

1. What is the purpose of concurrent programming?

2. What is the purpose of the Runnable interface in Java?

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Seção 3. Capítulo 1