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readme.md

☕ Java Lesson – Executor Framework in Java

Is lesson me hum seekhenge:

  • Executor kya hota hai
  • Executor vs Thread
  • Single Thread Executor
  • Multi Thread Executor (Thread Pool)
  • Future (result return)
  • Complete workflow

1️⃣ Executor Kya Hota Hai?

Executor ek framework hai jo:

thread creation aur management ko simplify karta hai

Package:

java.util.concurrent

2️⃣ Executor Kyun Use Karte Hain?

Problem with Thread:

❌ manually thread manage karna padta hai
❌ performance issue
❌ scalability problem

Solution:

✔ Executor framework use karo

3️⃣ Executor Interface

Executor executor = Executors.newSingleThreadExecutor();

4️⃣ Types of Executors

1. Single Thread Executor
2. Fixed Thread Pool
3. Cached Thread Pool

5️⃣ Single Thread Executor

✔ ek hi thread use hota hai
✔ tasks sequentially execute hote hain

import java.util.concurrent.*;

class Test {

    public static void main(String[] args){

        ExecutorService executor = Executors.newSingleThreadExecutor();

        executor.execute(() -> {
            System.out.println("Task 1");
        });

        executor.execute(() -> {
            System.out.println("Task 2");
        });

        executor.shutdown();
    }
}

6️⃣ Multi Thread Executor (Thread Pool)

ExecutorService executor = Executors.newFixedThreadPool(3);

✔ 3 threads ek saath kaam karenge

for(int i = 1; i <= 5; i++){

    int num = i;

    executor.execute(() -> {
        System.out.println("Task " + num + 
            " by " + Thread.currentThread().getName());
    });
}

7️⃣ Cached Thread Pool

ExecutorService executor = Executors.newCachedThreadPool();

✔ dynamic threads create karta hai

8️⃣ Runnable vs Callable

Feature Runnable Callable
Return ❌ No ✔ Yes
Exception ❌ No ✔ Yes

9️⃣ Future Kya Hota Hai?

Future ek object hai jo:

future result ko represent karta hai

🔟 Callable + Future Example

import java.util.concurrent.*;

class Test {

    public static void main(String[] args) throws Exception {

        ExecutorService executor = Executors.newSingleThreadExecutor();

        Callable<Integer> task = () -> {
            return 10 + 20;
        };

        Future<Integer> result = executor.submit(task);

        System.out.println(result.get()); // wait and get result

        executor.shutdown();
    }
}

1️⃣1️⃣ Future Methods

Method Use
get() result lena
isDone() task complete check
cancel() cancel task

1️⃣2️⃣ execute() vs submit()

Method Use
execute() Runnable
submit() Runnable + Callable

1️⃣3️⃣ Executor Lifecycle

1. create executor
2. submit task
3. execute task
4. shutdown

1️⃣4️⃣ Shutdown Methods

executor.shutdown();       // graceful shutdown
executor.shutdownNow();    // immediate stop

1️⃣5️⃣ Real-Life Analogy

Office me manager (Executor)
workers (threads)
tasks assign karta hai

1️⃣6️⃣ Advantages

✔ better performance
✔ thread reuse (thread pool)
✔ scalable
✔ easy management

1️⃣7️⃣ Important Points

✔ ExecutorService use karna best practice hai
✔ always shutdown executor
✔ Future async result handle karta hai

🎯 Interview Questions

  1. Executor framework kya hota hai?
  2. Runnable vs Callable difference?
  3. Future kya hota hai?
  4. Fixed thread pool kya hota hai?
  5. execute() vs submit()?

🧾 Lesson Summary

Is lesson me humne seekha:

✔ Executor framework concept
✔ Single thread executor
✔ Multi-thread (thread pool)
✔ Callable & Future
✔ Task management

Executor framework Java me modern aur efficient multithreading solution provide karta hai.