Implement something using multi-threading in Java

Let’s implement a simple Java program that demonstrates multithreading. We’ll create a scenario where multiple threads print numbers concurrently. This example will illustrate the basic principles of creating, starting, and managing threads in Java.

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Step-by-Step Implementation

1. Create a class that implements Runnable interface: This class will define the task that each thread will execute.
2. Create and start multiple threads: We will create instances of the Thread class, passing our Runnable implementation to the constructor.

Complete Code Example

// NumberPrinter.java
public class NumberPrinter implements Runnable {
    private String threadName;
    private int start;
    private int end;
    public NumberPrinter(String threadName, int start, int end) {
        this.threadName = threadName;
        this.start = start;
        this.end = end;
    }
    @Override
    public void run() {
        for (int i = start; i <= end; i++) {
            System.out.println(threadName + ": " + i);
            try {
                // Sleep for a bit to simulate work and make the output more readable
                Thread.sleep(100);
            } catch (InterruptedException e) {
                System.out.println(threadName + " interrupted.");
            }
        }
        System.out.println(threadName + " finished.");
    }
    public static void main(String[] args) {
        // Create instances of the Runnable task
        NumberPrinter printer1 = new NumberPrinter("Thread-1", 1, 10);
        NumberPrinter printer2 = new NumberPrinter("Thread-2", 11, 20);
        NumberPrinter printer3 = new NumberPrinter("Thread-3", 21, 30);
        // Create thread objects and pass the runnable tasks to them
        Thread thread1 = new Thread(printer1);
        Thread thread2 = new Thread(printer2);
        Thread thread3 = new Thread(printer3);
        // Start the threads
        thread1.start();
        thread2.start();
        thread3.start();
        // Wait for all threads to complete
        try {
            thread1.join();
            thread2.join();
            thread3.join();
        } catch (InterruptedException e) {
            System.out.println("Main thread interrupted.");
        }
        System.out.println("All threads finished.");
    }
}

Explanation

NumberPrinter Class:

• Implements the Runnable interface, allowing instances to be executed by a thread.
• The run method defines the code that constitutes the task of the thread. It prints numbers from start to end, prefixed by the thread's name.
• The constructor takes parameters for the thread name, start, and end numbers.

Main Method:

• Three instances of NumberPrinter are created, each configured to print a different range of numbers.
• Three Thread objects are created, each initialized with one of the NumberPrinter instances.
• The start method is called on each thread to begin execution.
• The join method is used to wait for all threads to complete before the main thread proceeds.

Running the Program

Compile and run the program using the following commands in your terminal or command prompt:

javac NumberPrinter.java
java NumberPrinter

You should see the output from each thread interleaved, demonstrating concurrent execution. Note that the exact order of output may vary each time you run the program, due to the nature of thread scheduling.