Java Threads Basics

What is a Thread?

A thread in Java is a lightweight process that can run concurrently with other threads.

Threads share the same memory space, which allows them to communicate more easily compared to separate processes.

Creating Threads

There are two primary ways to create threads in Java:

1. Extending the Thread class
2. Implementing the Runnable interface

1. Extending the Thread Class

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

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

2. Implementing the Runnable Interface

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

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

Thread Life Cycle

The life cycle of a thread can be represented in several states:

• New
• Runnable
• Blocked
• Waiting
• Timed Waiting
• Terminated

graph TD;
                A[New] -->|start()| B(Runnable);
                B -->|running| C[Blocked];
                C -->|releases lock| B;
                B -->|wait| D[Waiting];
                D -->|notify| B;
                B -->|sleep| E[Timed Waiting];
                E --> B;
                B -->|completion| F[Terminated];
            

Synchronization

Synchronization is necessary in multithreading to avoid data inconsistency. You can synchronize methods or blocks:

public synchronized void synchronizedMethod() {
    // synchronized code
}

Best Practices

• Minimize synchronization to improve performance.
• Use thread-safe collections from java.util.concurrent.
• Avoid using Thread.stop() to stop a thread.
• Prefer using ExecutorService over manually managing threads.