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How to Use Multithreading In Java?

7 minutes read

Multithreading in Java allows you to execute multiple threads simultaneously, enabling better performance and responsiveness in your applications. To create a multithreaded application in Java, you can extend the Thread class or implement the Runnable interface, overriding the run() method with the code you want to execute concurrently. You then create instances of your thread classes and start them using the start() method.


Java provides built-in support for synchronization mechanisms such as synchronized blocks, locks, and thread-safe collections to prevent data races and ensure thread safety. You can also use the wait(), notify(), and notifyAll() methods from the Object class to implement inter-thread communication and coordination.


When working with multithreading in Java, it is essential to be mindful of thread safety issues and potential race conditions that can occur when multiple threads access shared resources concurrently. Proper synchronization and coordination mechanisms should be used to prevent data corruption and ensure the correctness of your multithreaded code.

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How to create a new thread in Java?

In Java, you can create a new thread by either extending the Thread class or implementing the Runnable interface. Below are the steps to create a new thread using both approaches:

  1. Extending the Thread class: Create a new class that extends the Thread class and override the run() method. Implement the logic that you want to execute in the new thread inside the run() method. Create an instance of your custom thread class and call its start() method to start the thread.


Example:

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public class CustomThread extends Thread {
    public void run() {
        System.out.println("New thread is running");
    }

    public static void main(String[] args) {
        CustomThread myThread = new CustomThread();
        myThread.start();
    }
}


  1. Implementing the Runnable interface: Create a new class that implements the Runnable interface and implement the run() method. Implement the logic that you want to execute in the new thread inside the run() method. Create an instance of your custom Runnable class and pass it to a Thread instance as a parameter. Call the start() method on the Thread instance to start the new thread.


Example:

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public class CustomRunnable implements Runnable {
    public void run() {
        System.out.println("New thread is running");
    }

    public static void main(String[] args) {
        CustomRunnable myRunnable = new CustomRunnable();
        Thread myThread = new Thread(myRunnable);
        myThread.start();
    }
}


Both approaches will create a new thread that will execute the logic specified in the run() method concurrently with the main thread.


How to create and manage a Thread Pool in Java?

To create and manage a Thread Pool in Java, you can use the ExecutorService interface provided in the java.util.concurrent package. Here is a step-by-step guide on how to create and manage a Thread Pool in Java:

  1. Create a ThreadPoolExecutor instance:
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ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);


This will create a fixed-size ThreadPoolExecutor with the specified number of threads.

  1. Submit tasks to the thread pool:
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executor.submit(new RunnableTask());


You can submit tasks to the thread pool using the submit() method. RunnableTask is a class that implements the Runnable interface and contains the code that you want to run in a separate thread.

  1. Shutdown the thread pool:
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executor.shutdown();


After submitting all the tasks, you should shut down the thread pool using the shutdown() method. This will initiate an orderly shutdown of the thread pool, allowing all submitted tasks to complete before shutting down the executor.

  1. Handle rejected tasks: If the thread pool is full and cannot accept any more tasks, you can handle rejected tasks by implementing a custom RejectedExecutionHandler and setting it on the ThreadPoolExecutor instance:
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executor.setRejectedExecutionHandler(new CustomRejectedExecutionHandler());


  1. Monitor the status of the thread pool: You can monitor the status of the thread pool by using the isShutdown() and isTerminated() methods:
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if(executor.isShutdown()) {
    System.out.println("Thread pool is shut down");
}
if(executor.isTerminated()) {
    System.out.println("All tasks have completed");
}


By following these steps, you can create and manage a Thread Pool in Java using the ExecutorService interface. This will help you efficiently manage multiple tasks and execute them concurrently using a fixed number of threads.


How to implement multithreading in Java?

There are several ways to implement multithreading in Java:

  1. Extending the Thread class: Create a new class that extends the Thread class and override the run() method to define the code that will be executed concurrently.
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class MyThread extends Thread {
    public void run() {
        // code to be executed concurrently
    }
}

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


  1. Implementing the Runnable interface: Create a class that implements the Runnable interface and define the code that will be executed concurrently in the run() method. Then create a new Thread object and pass an instance of the class to the Thread constructor.
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class MyRunnable implements Runnable {
    public void run() {
        // code to be executed concurrently
    }
}

public class Main {
    public static void main(String[] args) {
        MyRunnable myRunnable = new MyRunnable();
        Thread thread = new Thread(myRunnable);
        thread.start(); // start the thread
    }
}


  1. Using lambda expressions: With Java 8, you can also use lambda expressions to create and start threads easily.
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public class Main {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> {
            // code to be executed concurrently
        });
        thread.start(); // start the thread
    }
}


  1. Using Executor framework: The Executor framework provides a more flexible and efficient way to manage threads by separating the task creation and task execution. You can create an ExecutorService object and submit tasks to it using the submit() method.
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import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Main {
    public static void main(String[] args) {
        ExecutorService executor = Executors.newFixedThreadPool(5); // create a thread pool with 5 threads
        executor.submit(() -> {
            // code to be executed concurrently
        });
        executor.shutdown(); // shut down the executor
    }
}


These are some of the ways to implement multithreading in Java. Choose the one that best suits your requirements and design your application accordingly.

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