Creating Threads

There are 3 main ways to create a Thread:

Extending Thread Class

class MyThread extends Thread {
    public void run() {
        System.out.println("Running in MyThread");
    }
}
 
MyThread t1 = new MyThread();
t1.start(); // Always use start(), not run()
// Less flexible (can't extend other classes)

Implementing Runnable Interface - Recommended

class MyRunnable implements Runnable {
    public void run() {
        System.out.println("Running in Runnable");
    }
}
 
Thread t2 = new Thread(new MyRunnable());
t2.start();
// Better for reusability, preferred in modern Java

Using Callable + Future (With Executor)

Callable<String> task = () -> {
    return "Result from thread";
};
 
ExecutorService executor = Executors.newSingleThreadExecutor();
Future<String> future = executor.submit(task);
 
String result = future.get(); // blocks until result is ready
executor.shutdown();
// Returns a result + Can throw checked exceptions

Comparison

run() vs start()

Method	What It Does
run()	Runs code in the current thread
start()	Starts a new thread, runs run() internally

Real-World Use

Approach	Use When…
Thread	Quick + simple threading, one-off usage
Runnable	Commonly used in real apps & frameworks
Callable	You need a return value from the thread
Executors	Managing multiple threads efficiently

Tip

Be ready to:

• write class using Runnable or Callable,
• explain start() vs run(),
• talk about when to use ExecutorService (thread pools)

---

Parent: _Multithreading