Multithreading in Java is a programming technique that enables multiple threads to run concurrently within a single process. A thread is a single sequential flow of control within a process. In other words, it is a unit of execution in a process.

Advantages of multithreading

Let’s see what the advantages of multithreading are.

• Improved application performance - Multithreading allows multiple tasks to run simultaneously, which can improve the overall performance of an application;
• Better resource utilization - Multithreading enables an application to run more efficiently by utilizing available resources more effectively;
• Better responsiveness - Multithreading can improve the responsiveness of an application by allowing it to perform multiple tasks simultaneously.

How to create threads

To create a thread in Java, you can either extend the Thread class or implement the Runnable interface. The Thread class is a class in Java that provides a basic implementation of a thread, while the Runnable interface is a functional interface that defines a single method, run, which is the entry point for a thread.

Using the Thread class

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

Using the Runnable interface

Here's an example of creating a thread by implementing the Runnable interface.

Starting a thread

To start a thread in Java, you must call its start() method. This method will start the execution of the run method, which is the entry point for the thread. The run method contains the code that the thread will execute. Here's an example of how to start a thread:

Synchronization in Java

Synchronization in Java is a technique that controls access to shared resources by multiple threads. When multiple threads try to access the same resource, they may interfere with each other and cause unexpected results. Synchronization in Java avoids these problems by ensuring that only one thread can access a shared resource simultaneously. The synchronized keyword in Java is used to synchronize access to shared resources by multiple threads. When a method is marked as synchronized, only one thread can execute that method at a time. Here's an example of how to use the synchronized keyword.

Using the Executor framework

The Executor framework in Java solves the problem of managing and executing tasks concurrently in a scalable and efficient manner. Without the Executor framework, a common approach for executing tasks concurrently is manually creating and managing threads. This approach can be error-prone, difficult to manage, and lead to problems such as resource starvation, deadlocks, and other concurrency-related issues.

The Executor framework provides a higher-level abstraction over threads, allowing developers to submit tasks for execution without having to worry about the underlying details of creating and managing threads. This makes writing concurrent and scalable applications easier, as the framework takes care of the complexities of concurrent execution for you.

Additionally, the Executor framework provides a pool of reusable threads, reducing the overhead of creating and destroying threads for each task. This can improve the performance and scalability of the application.

Here's a simple code sample demonstrating how to use an Executor to execute a Runnable task.

In this example, we create a fixed-size thread pool with 2 threads using Executors.newFixedThreadPool(2). We then submit a RunnableTask for execution using the execute method of the Executor. The task will be executed asynchronously in one of the threads in the thread pool.

Conclusion

Multithreading in Java is a powerful technique that enables multiple threads to run concurrently within a single process, improving an application's overall performance and responsiveness. Java provides several classes and interfaces in the java.util.concurrent package to help you implement multithreading in your application. With the help of these classes and interfaces, you can easily create and synchronize threads and execute tasks in a multithreaded environment.