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What is Multithreading

Multithreading is a core concept in Java programming, and understanding it will significantly enhance your ability to create efficient applications. Multithreading refers to the concurrent execution of more than one sequential set (thread) of instructions.

Each thread in a process has its own program counter, stack, and local variables. Threads within the same process share the same memory space, allowing them to communicate with each other more easily than if they were separate processes.

Let's discuss the key elements:

Threads in Java​

A thread is a lightweight, smallest part of a process that can run concurrently with other parts (threads) of the same process. Threads are independent, so they do not affect the execution of another thread. A single process can contain multiple threads.

Java provides built-in support for multithreaded programming. A multithreaded program contains two or more parts that can run concurrently. Each part of such a program is called a thread, and each thread defines a separate path of execution.

Why Use Multithreading?​

Multithreading can be used in Java for the following reasons:

  • To perform complex tasks while keeping the user interface responsive: A single-threaded application could become unresponsive while it performs a lengthy operation. By using a separate thread for each large task, the application can continue to respond to user input.
  • To perform many tasks simultaneously: Some tasks are independent of others. For example, a word processor can format text at the same time that it is printing, provided these two operations are performed by separate threads.
  • To simplify program structure: A program that does several asynchronous tasks can be more easily organized as a set of threads, each of which is responsible for a single task.

Creating a Thread in Java​

In Java, there are two ways to create a thread:

  1. By extending the Thread class: The Thread class provides constructors and methods to create and perform operations on a thread. Thread is a class of java.lang package.
  2. By implementing the Runnable interface: If we are extending the Thread class, multiple inheritances may not be possible. However, this can be achieved by implementing the Runnable interface.

Multithreading Life Cycle​

The life cycle of threads in Java is controlled by JVM. The java thread states are as follows:

  1. New: The thread is in new state if you create an instance of Thread class but before the invocation of start() method.
  2. Runnable: The thread is in runnable state after invocation of start() method, but the thread scheduler has not selected it to be the running thread.
  3. Running: The thread is in running state if the thread scheduler has selected it.
  4. Non-Runnable (Blocked): This is the state when the thread is still alive, but is currently not eligible to run.
  5. Terminated (Dead): A thread is in terminated or dead state when its run() method exits.

Understanding the life cycle of threads will help you to manage them efficiently in your program.

In conclusion, multithreading in Java is a feature that allows concurrent execution of two or more parts of a program for maximum utilization of CPU. It is an essential concept for any aspiring Java developer.

In the next sections, we will explore more about how to create, control and manage threads in Java. We will also learn about thread synchronization and communication between threads.