Concurrency is an important concept in Java that deals with executing multiple tasks simultaneously. It involves the division of tasks into smaller subtasks that can be executed independently or concurrently. Multithreading is one of the key features in Java that enables concurrent programming.

In Java, a thread is a lightweight process that executes a series of instructions independently of other threads. Threads can be used to perform multiple tasks concurrently, allowing for efficient utilization of system resources.

To create and start a new thread in Java, you can implement the Runnable interface and override the run() method. The run() method contains the code that will be executed by the thread. Here's an example:

1public class Main {
2  public static void main(String[] args) {
3    Thread thread1 = new Thread(() -> {
4      for (int i = 1; i <= 10; i++) {
5        System.out.println("Thread 1: " + i);
6        try {
7          Thread.sleep(1000);
8        } catch (InterruptedException e) {
9          e.printStackTrace();
10        }
11      }
12    });
13
14    Thread thread2 = new Thread(() -> {
15      for (int i = 1; i <= 10; i++) {
16        System.out.println("Thread 2: " + i);
17        try {
18          Thread.sleep(1000);
19        } catch (InterruptedException e) {
20          e.printStackTrace();
21        }
22      }
23    });
24
25    thread1.start();
26    thread2.start();
27  }
28}

In the above example, we create two threads (thread1 and thread2) and define their behavior using lambda expressions. Each thread prints numbers from 1 to 10, with a delay of 1 second between each iteration. The Thread.sleep() method is used to pause the execution of a thread for a specified duration.

When we start the threads using start(), they run concurrently and may produce interleaved output.

Understanding concurrency and multithreading is crucial in Java development, especially when building scalable and performant applications. It allows for efficient utilization of system resources and improved responsiveness.

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public class Main {

  public static void main(String[] args) {

    // replace with your Java logic here

    Thread thread1 = new Thread(() -> {

      for (int i = 1; i <= 10; i++) {

        System.out.println("Thread 1: " + i);

        try {

          Thread.sleep(1000);

        } catch (InterruptedException e) {

          e.printStackTrace();

        }

      }

    });

​

    Thread thread2 = new Thread(() -> {

      for (int i = 1; i <= 10; i++) {

        System.out.println("Thread 2: " + i);

        try {

          Thread.sleep(1000);

        } catch (InterruptedException e) {

          e.printStackTrace();

        }

      }

    });

​

    thread1.start();

    thread2.start();

  }

}