Android Multithreading Java Samples

// Android Java Thread Creation Examples
// Using Thread, Runnable, and ExecutorService

import android.os.Handler;
import android.os.Looper;
import java.util.concurrent.*;

// 1. Basic Thread Creation
class BasicThreadCreation {

    // Create thread using Thread class
    public void createBasicThread() {
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("Thread running: " + Thread.currentThread().getName());
                // Perform background work
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Thread completed");
            }
        });

        thread.start();
    }

    // Create thread with custom name
    public void createNamedThread(String name) {
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("Named thread: " + Thread.currentThread().getName());
                // Perform work
            }
        }, name);

        thread.start();
    }

    // Create thread using Runnable
    public void createThreadWithRunnable() {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                System.out.println("Runnable thread: " + Thread.currentThread().getName());
            }
        };

        Thread thread = new Thread(runnable);
        thread.start();
    }

    // Create thread using lambda (Java 8+)
    public void createThreadWithLambda() {
        Thread thread = new Thread(() -> {
            System.out.println("Lambda thread: " + Thread.currentThread().getName());
            performWork();
        });

        thread.start();
    }

    private void performWork() {
        // Simulate work
        try {
            Thread.sleep(500);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Work completed");
    }
}

// 2. Thread with Exception Handling
class ThreadExceptionHandling {

    public void createThreadWithExceptionHandling() {
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    System.out.println("Thread working...");
                    // Simulate error
                    throw new RuntimeException("Thread error!");
                } catch (Exception e) {
                    System.out.println("Caught exception in thread: " + e.getMessage());
                }
            }
        });

        thread.setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
            @Override
            public void uncaughtException(Thread t, Throwable e) {
                System.out.println("Uncaught exception in " + t.getName() + ": " + e.getMessage());
            }
        });

        thread.start();
    }

    // Thread with priority
    public void createThreadWithPriority() {
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("High priority thread running");
            }
        });

        thread.setPriority(Thread.MAX_PRIORITY);
        thread.start();
    }

    // Daemon thread
    public void createDaemonThread() {
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                int count = 0;
                while (true) {
                    System.out.println("Daemon thread: " + count);
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        break;
                    }
                    count++;
                }
            }
        });

        thread.setDaemon(true);
        thread.start();

        // Main thread exits, daemon thread terminates
    }

    // Thread sleep and join
    public void createThreadWithJoin() {
        final Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("Thread 1 starting");
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Thread 1 completed");
            }
        });

        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("Thread 2 starting");
                try {
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Thread 2 completed");
            }
        });

        thread1.start();
        thread2.start();

        // Wait for both threads to complete
        try {
            thread1.join();
            thread2.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println("All threads completed");
    }
}

// 3. Handler and Looper (Android Specific)
class HandlerLooperExample {

    private final Handler handler = new Handler(Looper.getMainLooper());

    // Post runnable to main thread
    public void postToMainThread() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("Background thread: " + Thread.currentThread().getName());

                // Post result to main thread
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        System.out.println("Main thread: " + Thread.currentThread().getName());
                        // Update UI
                    }
                });
            }
        }).start();
    }

    // Post delayed
    public void postDelayed() {
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                System.out.println("Delayed execution on main thread");
            }
        }, 2000); // 2 seconds delay
    }

    // Post at front of queue
    public void postAtFrontOfQueue() {
        handler.postAtFrontOfQueue(new Runnable() {
            @Override
            public void run() {
                System.out.println("Execute immediately on main thread");
            }
        });
    }

    // Remove callbacks
    public void removeCallbacks() {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                System.out.println("This won't execute");
            }
        };

        handler.post(runnable);
        handler.removeCallbacks(runnable);
    }
}

// 4. Thread Communication (Wait and Notify)
class ThreadCommunication {

    private String sharedData = "";

    public void waitNotifyExample() {
        final Object lock = new Object();

        Thread producerThread = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (lock) {
                    System.out.println("Producer: Producing data...");
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    sharedData = "Hello from producer";
                    System.out.println("Producer: Data ready, notifying...");
                    lock.notifyAll();
                }
            }
        });

        Thread consumerThread = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (lock) {
                    System.out.println("Consumer: Waiting for data...");
                    while (sharedData.isEmpty()) {
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                    System.out.println("Consumer: Received: " + sharedData);
                }
            }
        });

        consumerThread.start();
        producerThread.start();
    }
}

// 5. Thread Local Storage
class ThreadLocalStorageExample {

    private ThreadLocal<String> threadLocal = new ThreadLocal<>();

    public void threadLocalDemo() {
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                threadLocal.set("Value from Thread 1");
                System.out.println("Thread 1: " + threadLocal.get());
            }
        });

        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                threadLocal.set("Value from Thread 2");
                System.out.println("Thread 2: " + threadLocal.get());
            }
        });

        thread1.start();
        thread2.start();

        try {
            thread1.join();
            thread2.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println("Main thread: " + threadLocal.get());
    }
}

// 6. AsyncTask (Deprecated but still useful for understanding)
// Note: AsyncTask is deprecated in API 30, use Coroutines or ExecutorService instead
class ModernAsyncExample {

    private final ExecutorService executor = Executors.newFixedThreadPool(4);
    private final Handler handler = new Handler(Looper.getMainLooper());

    // Modern approach using ExecutorService and Handler
    public void executeAsyncTask() {
        executor.execute(new Runnable() {
            @Override
            public void run() {
                // Background work
                System.out.println("Working in background: " + Thread.currentThread().getName());
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                // Post result to main thread
                final String result = "Task completed";
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        System.out.println("Result on main thread: " + result);
                        // Update UI here
                    }
                });
            }
        });
    }

    // Cancelable task
    public Future<String> submitCancelableTask() {
        Future<String> future = executor.submit(new Callable<String>() {
            @Override
            public String call() throws Exception {
                System.out.println("Task started");
                for (int i = 0; i < 10; i++) {
                    Thread.sleep(200);
                    System.out.println("Progress: " + (i + 1) * 10 + "%");
                }
                return "Task completed successfully";
            }
        });

        return future;
    }

    public void shutdown() {
        executor.shutdown();
    }
}

// Main demonstration
class ThreadCreationDemo {
    public static void demonstrateThreadCreation() {
        System.out.println("=== Android Java Thread Creation Examples ===\n");

        // 1. Basic thread creation
        System.out.println("--- 1. Basic Thread Creation ---");
        BasicThreadCreation basicThread = new BasicThreadCreation();
        basicThread.createBasicThread();
        basicThread.createNamedThread("MyCustomThread");

        // 2. Lambda thread
        System.out.println("\n--- 2. Lambda Thread ---");
        basicThread.createThreadWithLambda();

        // 3. Exception handling
        System.out.println("\n--- 3. Exception Handling ---");
        ThreadExceptionHandling exceptionHandling = new ThreadExceptionHandling();
        exceptionHandling.createThreadWithJoin();

        // 4. Handler and Looper
        System.out.println("\n--- 4. Handler and Looper ---");
        HandlerLooperExample handlerExample = new HandlerLooperExample();
        handlerExample.postToMainThread();

        // 5. Thread communication
        System.out.println("\n--- 5. Thread Communication ---");
        ThreadCommunication communication = new ThreadCommunication();
        communication.waitNotifyExample();

        // Wait for threads to complete
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println("\n=== All Thread Creation Examples Completed ===");
    }
}

// Android Java Thread Synchronization Examples
// Using locks, semaphores, and synchronization mechanisms

import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
import java.util.concurrent.locks.*;

// 1. Synchronized Block and Method
class SynchronizedBlockExample {
    private int counter = 0;

    // Using synchronized block
    public void incrementCounter() {
        synchronized (this) {
            counter++;
            System.out.println("Counter: " + counter + " (Thread: " + Thread.currentThread().getName() + ")");
        }
    }

    // Synchronized method
    public synchronized void decrementCounter() {
        counter--;
        System.out.println("Counter: " + counter + " (Thread: " + Thread.currentThread().getName() + ")");
    }

    public synchronized int getCounter() {
        return counter;
    }
}

// 2. ReentrantLock
class ReentrantLockExample {
    private final Lock lock = new ReentrantLock();
    private int sharedResource = 0;

    public void performTask() {
        lock.lock();
        try {
            System.out.println("Lock acquired by " + Thread.currentThread().getName());
            // Critical section
            sharedResource++;
            Thread.sleep(100);
            System.out.println("Shared resource: " + sharedResource);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
            System.out.println("Lock released by " + Thread.currentThread().getName());
        }
    }

    public void tryLockExample() {
        try {
            if (lock.tryLock(1, TimeUnit.SECONDS)) {
                try {
                    System.out.println("TryLock succeeded");
                    // Perform work
                } finally {
                    lock.unlock();
                }
            } else {
                System.out.println("Could not acquire lock");
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    // ReadWriteLock for multiple readers
    private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
    private String data = "Initial Data";

    public String readData() {
        readWriteLock.readLock().lock();
        try {
            System.out.println("Reading: " + data);
            return data;
        } finally {
            readWriteLock.readLock().unlock();
        }
    }

    public void writeData(String newValue) {
        readWriteLock.writeLock().lock();
        try {
            System.out.println("Writing: " + newValue);
            data = newValue;
        } finally {
            readWriteLock.writeLock().unlock();
        }
    }
}

// 3. Semaphore
class SemaphoreExample {
    private final Semaphore semaphore = new Semaphore(3); // Allow 3 concurrent accesses

    public void accessResource(int id) {
        try {
            semaphore.acquire();
            System.out.println("Resource " + id + " acquired by " + Thread.currentThread().getName());

            // Simulate work
            Thread.sleep(1000);
            System.out.println("Resource " + id + " released");
        } catch (InterruptedException e) {
            System.out.println("Interrupted: " + e.getMessage());
        } finally {
            semaphore.release();
        }
    }

    public void tryAcquireExample(int id) {
        if (semaphore.tryAcquire()) {
            try {
                System.out.println("Resource " + id + " accessed immediately");
                Thread.sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                semaphore.release();
            }
        } else {
            System.out.println("Resource " + id + " not available");
        }
    }
}

// 4. Atomic Variables
class AtomicVariableExample {
    private final AtomicInteger atomicCounter = new AtomicInteger(0);
    private final AtomicBoolean atomicBoolean = new AtomicBoolean(false);
    private final AtomicReference<String> atomicReference = new AtomicReference<>("Initial");

    public void atomicIncrement() {
        int newValue = atomicCounter.incrementAndGet();
        System.out.println("Atomic counter: " + newValue);
    }

    public void compareAndSet() {
        boolean success = atomicBoolean.compareAndSet(false, true);
        System.out.println("CAS result: " + success + ", Value: " + atomicBoolean.get());
    }

    public void atomicUpdate() {
        atomicReference.updateAndGet(current -> {
            System.out.println("Current: " + current);
            return "Updated";
        });
        System.out.println("Final: " + atomicReference.get());
    }

    public void getAndAdd() {
        int oldValue = atomicCounter.getAndAdd(5);
        System.out.println("Old: " + oldValue + ", New: " + atomicCounter.get());
    }
}

// 5. CountDownLatch
class CountDownLatchExample {
    public void demonstrateLatch() {
        final CountDownLatch latch = new CountDownLatch(3);

        // Create worker threads
        for (int i = 0; i < 3; i++) {
            final int index = i;
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        System.out.println("Worker " + index + " starting");
                        Thread.sleep(1000 + (int)(Math.random() * 1000));
                        System.out.println("Worker " + index + " completed");
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    } finally {
                        latch.countDown();
                    }
                }
            }).start();
        }

        // Main thread waits
        System.out.println("Main thread waiting for workers...");
        try {
            latch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("All workers completed!");
    }

    public void awaitWithTimeout() {
        final CountDownLatch latch = new CountDownLatch(5);

        for (int i = 0; i < 5; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    } finally {
                        latch.countDown();
                    }
                }
            }).start();
        }

        // Wait with timeout
        try {
            if (latch.await(2, TimeUnit.SECONDS)) {
                System.out.println("Completed within timeout");
            } else {
                System.out.println("Timeout - not all completed");
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

// 6. CyclicBarrier
class CyclicBarrierExample {
    public void demonstrateBarrier() {
        final CyclicBarrier barrier = new CyclicBarrier(3, new Runnable() {
            @Override
            public void run() {
                System.out.println("\n*** All threads reached barrier ***\n");
            }
        });

        for (int i = 0; i < 3; i++) {
            final int index = i;
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        System.out.println("Thread " + index + ": Phase 1");
                        Thread.sleep(500);
                        System.out.println("Thread " + index + ": Waiting at barrier");

                        barrier.await();

                        System.out.println("Thread " + index + ": Phase 2");
                    } catch (Exception e) {
                        System.out.println("Barrier error: " + e.getMessage());
                    }
                }
            }).start();
        }
    }
}

// 7. BlockingQueue (Producer-Consumer)
class BlockingQueueExample {
    private final BlockingQueue<Integer> queue = new ArrayBlockingQueue<>(5);
    private volatile boolean running = true;

    public void startProducer() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                int item = 0;
                while (running) {
                    try {
                        queue.put(item);
                        System.out.println("Produced: " + item + " (Queue size: " + queue.size() + ")");
                        item++;
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        break;
                    }
                }
            }
        }).start();
    }

    public void startConsumer() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (running) {
                    try {
                        int item = queue.take();
                        System.out.println("Consumed: " + item);
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        break;
                    }
                }
            }
        }).start();
    }

    public void stop() {
        running = false;
    }
}

// 8. Volatile Variables
class VolatileExample {
    private volatile boolean flag = false;

    public void startFlagWatcher() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("Watcher: Waiting for flag...");
                while (!flag) {
                    // Busy wait (not recommended, use proper synchronization)
                }
                System.out.println("Watcher: Flag is now true!");
            }
        }).start();
    }

    public void setFlag() {
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        flag = true;
        System.out.println("Main: Flag set to true");
    }
}

// 9. Thread-safe Collections
class ThreadSafeCollectionsExample {
    // ConcurrentHashMap
    private final ConcurrentHashMap<String, Integer> concurrentMap = new ConcurrentHashMap<>();

    public void addToConcurrentMap() {
        for (int i = 0; i < 10; i++) {
            final int index = i;
            new Thread(new Runnable() {
                @Override
                public void run() {
                    concurrentMap.put("key" + index, index);
                    System.out.println("Added key" + index + ": " + index);
                }
            }).start();
        }

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Map size: " + concurrentMap.size());
    }

    // CopyOnWriteArrayList
    private final CopyOnWriteArrayList<String> concurrentList = new CopyOnWriteArrayList<>();

    public void addToList() {
        for (int i = 0; i < 5; i++) {
            final int index = i;
            new Thread(new Runnable() {
                @Override
                public void run() {
                    concurrentList.add("Item " + index);
                    System.out.println("List size: " + concurrentList.size());
                }
            }).start();
        }

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("List: " + concurrentList);
    }

    // Concurrent Linked Queue
    private final ConcurrentLinkedQueue<Integer> concurrentQueue = new ConcurrentLinkedQueue<>();

    public void addToQueue() {
        for (int i = 0; i < 5; i++) {
            final int index = i;
            new Thread(new Runnable() {
                @Override
                public void run() {
                    concurrentQueue.offer(index);
                    System.out.println("Queue size: " + concurrentQueue.size());
                }
            }).start();
        }

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Queue: " + concurrentQueue);
    }
}

// Main demonstration
class ThreadSynchronizationDemo {
    public static void demonstrateThreadSynchronization() {
        System.out.println("=== Android Java Thread Synchronization Examples ===\n");

        // 1. Synchronized block
        System.out.println("--- 1. Synchronized Block ---");
        final SynchronizedBlockExample syncExample = new SynchronizedBlockExample();

        for (int i = 0; i < 5; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    syncExample.incrementCounter();
                }
            }).start();
        }

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 2. ReentrantLock
        System.out.println("\n--- 2. ReentrantLock ---");
        final ReentrantLockExample lockExample = new ReentrantLockExample();

        for (int i = 0; i < 3; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    lockExample.performTask();
                }
            }).start();
        }

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 3. Semaphore
        System.out.println("\n--- 3. Semaphore ---");
        final SemaphoreExample semaphoreExample = new SemaphoreExample();

        for (int i = 0; i < 5; i++) {
            final int index = i;
            new Thread(new Runnable() {
                @Override
                public void run() {
                    semaphoreExample.accessResource(index);
                }
            }).start();
        }

        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 4. Atomic variables
        System.out.println("\n--- 4. Atomic Variables ---");
        final AtomicVariableExample atomicExample = new AtomicVariableExample();

        for (int i = 0; i < 5; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    atomicExample.atomicIncrement();
                }
            }).start();
        }

        try {
            Thread.sleep(500);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 5. CountDownLatch
        System.out.println("\n--- 5. CountDownLatch ---");
        CountDownLatchExample latchExample = new CountDownLatchExample();
        latchExample.demonstrateLatch();

        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 6. Thread-safe collections
        System.out.println("\n--- 6. Thread-safe Collections ---");
        ThreadSafeCollectionsExample collectionsExample = new ThreadSafeCollectionsExample();
        collectionsExample.addToConcurrentMap();

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println("\n=== All Thread Synchronization Examples Completed ===");
    }
}

// Android Java Thread Pool Examples
// Using ExecutorService, Custom Thread Pools, and Future

import java.util.concurrent.*;
import java.util.List;
import java.util.ArrayList;

// 1. ExecutorService Thread Pools
class ExecutorServicePools {

    // Fixed thread pool
    public void fixedThreadPoolExample() {
        ExecutorService executor = Executors.newFixedThreadPool(4);

        System.out.println("--- Fixed Thread Pool (4 threads) ---");

        long startTime = System.currentTimeMillis();

        List<Future<Void>> futures = new ArrayList<>();
        for (int taskId = 1; taskId <= 8; taskId++) {
            final int finalTaskId = taskId;
            Future<Void> future = executor.submit(new Callable<Void>() {
                @Override
                public Void call() throws Exception {
                    System.out.println("Task " + finalTaskId + " starting on " + Thread.currentThread().getName());
                    Thread.sleep(1000);
                    System.out.println("Task " + finalTaskId + " completed");
                    return null;
                }
            });
            futures.add(future);
        }

        // Wait for all tasks to complete
        for (Future<Void> future : futures) {
            try {
                future.get();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        long endTime = System.currentTimeMillis();
        System.out.println("Total time: " + (endTime - startTime) + "ms");

        executor.shutdown();
    }

    // Cached thread pool
    public void cachedThreadPoolExample() {
        ExecutorService executor = Executors.newCachedThreadPool();

        System.out.println("\n--- Cached Thread Pool ---");

        List<Future<Integer>> futures = new ArrayList<>();
        for (int taskId = 1; taskId <= 10; taskId++) {
            final int finalTaskId = taskId;
            Future<Integer> future = executor.submit(new Callable<Integer>() {
                @Override
                public Integer call() throws Exception {
                    System.out.println("Task " + finalTaskId + " on " + Thread.currentThread().getName());
                    Thread.sleep(100 + (int)(Math.random() * 400));
                    return finalTaskId * 2;
                }
            });
            futures.add(future);
        }

        for (Future<Integer> future : futures) {
            try {
                Integer result = future.get();
                System.out.println("Result: " + result);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        executor.shutdown();
    }

    // Single thread executor
    public void singleThreadExecutorExample() {
        ExecutorService executor = Executors.newSingleThreadExecutor();

        System.out.println("\n--- Single Thread Executor ---");

        for (int taskId = 1; taskId <= 5; taskId++) {
            final int finalTaskId = taskId;
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    System.out.println("Task " + finalTaskId + " on " + Thread.currentThread().getName());
                    try {
                        Thread.sleep(200);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            });
        }

        executor.shutdown();
        try {
            executor.awaitTermination(5, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    // Scheduled executor
    public void scheduledExecutorExample() {
        ScheduledExecutorService executor = Executors.newScheduledThreadPool(2);

        System.out.println("\n--- Scheduled Executor ---");

        // Schedule one-time task
        executor.schedule(new Runnable() {
            @Override
            public void run() {
                System.out.println("Delayed task executed");
            }
        }, 2, TimeUnit.SECONDS);

        // Schedule at fixed rate
        final ScheduledFuture<?> future = executor.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                System.out.println("Periodic task at " + System.currentTimeMillis());
            }
        }, 0, 1, TimeUnit.SECONDS);

        // Run for 5 seconds then shutdown
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        future.cancel(true);
        executor.shutdown();
    }
}

// 2. Custom Thread Pool
class CustomThreadPoolExample {

    public void customThreadPoolExample() {
        // Create custom thread pool
        ThreadFactory threadFactory = new ThreadFactory() {
            private int count = 0;

            @Override
            public Thread newThread(Runnable r) {
                Thread thread = new Thread(r);
                thread.setName("CustomPool-" + System.currentTimeMillis() + "-" + count++);
                thread.setDaemon(false);
                thread.setPriority(Thread.NORM_PRIORITY);
                return thread;
            }
        };

        ThreadPoolExecutor executor = new ThreadPoolExecutor(
            2, // Core pool size
            5, // Maximum pool size
            60L, // Keep-alive time
            TimeUnit.SECONDS,
            new LinkedBlockingQueue<Runnable>(10), // Work queue
            threadFactory,
            new ThreadPoolExecutor.CallerRunsPolicy() // Rejection policy
        );

        System.out.println("\n--- Custom Thread Pool ---");

        // Submit tasks
        for (int i = 1; i <= 10; i++) {
            final int taskId = i;
            try {
                executor.execute(new Runnable() {
                    @Override
                    public void run() {
                        System.out.println("Task " + taskId + " on " + Thread.currentThread().getName());
                        try {
                            Thread.sleep(500);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                });
            } catch (RejectedExecutionException e) {
                System.out.println("Task " + i + " rejected");
            }
        }

        executor.shutdown();
        try {
            executor.awaitTermination(10, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

// 3. ExecutorService with Future
class FutureExample {

    public void submitWithFuture() {
        ExecutorService executor = Executors.newFixedThreadPool(3);

        System.out.println("\n--- ExecutorService with Future ---");

        // Submit callable tasks
        List<Future<Integer>> futures = new ArrayList<>();
        for (int taskId = 1; taskId <= 5; taskId++) {
            final int finalTaskId = taskId;
            Future<Integer> future = executor.submit(new Callable<Integer>() {
                @Override
                public Integer call() throws Exception {
                    System.out.println("Task " + finalTaskId + " starting");
                    Thread.sleep(500 + (int)(Math.random() * 1000));
                    System.out.println("Task " + finalTaskId + " completed");
                    return finalTaskId * 10;
                }
            });
            futures.add(future);
        }

        // Process results as they complete
        for (Future<Integer> future : futures) {
            try {
                Integer result = future.get();
                System.out.println("Future result: " + result);
            } catch (Exception e) {
                System.out.println("Future error: " + e.getMessage());
            }
        }

        executor.shutdown();
    }

    public void invokeAllExample() {
        ExecutorService executor = Executors.newFixedThreadPool(4);

        List<Callable<Integer>> tasks = new ArrayList<>();
        for (int taskId = 1; taskId <= 10; taskId++) {
            final int finalTaskId = taskId;
            tasks.add(new Callable<Integer>() {
                @Override
                public Integer call() throws Exception {
                    Thread.sleep(1000);
                    return finalTaskId;
                }
            });
        }

        long startTime = System.currentTimeMillis();

        try {
            List<Future<Integer>> futures = executor.invokeAll(tasks);

            for (Future<Integer> future : futures) {
                System.out.println("Completed: " + future.get());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        long endTime = System.currentTimeMillis();
        System.out.println("InvokeAll time: " + (endTime - startTime) + "ms");

        executor.shutdown();
    }

    public void invokeAnyExample() {
        ExecutorService executor = Executors.newFixedThreadPool(4);

        List<Callable<Integer>> tasks = new ArrayList<>();
        for (int taskId = 1; taskId <= 5; taskId++) {
            final int finalTaskId = taskId;
            tasks.add(new Callable<Integer>() {
                @Override
                public Integer call() throws Exception {
                    int sleepTime = (int)(Math.random() * 3000) + 1000;
                    System.out.println("Task " + finalTaskId + " will take " + sleepTime + "ms");
                    Thread.sleep(sleepTime);
                    return finalTaskId;
                }
            });
        }

        try {
            Integer result = executor.invokeAny(tasks);
            System.out.println("First completed task: " + result);
        } catch (Exception e) {
            e.printStackTrace();
        }

        executor.shutdown();
    }
}

// 4. Completion Service
class CompletionServiceExample {

    public void completionServiceDemo() {
        ExecutorService executor = Executors.newFixedThreadPool(4);
        CompletionService<Integer> completionService = new ExecutorCompletionService<>(executor);

        System.out.println("\n--- Completion Service ---");

        // Submit tasks
        for (int taskId = 1; taskId <= 5; taskId++) {
            final int finalTaskId = taskId;
            completionService.submit(new Callable<Integer>() {
                @Override
                public Integer call() throws Exception {
                    int sleepTime = 1000 + (int)(Math.random() * 2000);
                    System.out.println("Task " + finalTaskId + " will take " + sleepTime + "ms");
                    Thread.sleep(sleepTime);
                    return finalTaskId;
                }
            });
        }

        // Process as they complete
        for (int i = 0; i < 5; i++) {
            try {
                Future<Integer> future = completionService.take();
                Integer result = future.get();
                System.out.println("Completed task: " + result);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        executor.shutdown();
    }
}

// 5. ForkJoin Pool (Parallel processing)
class ForkJoinPoolExample {

    public void parallelSum() {
        ForkJoinPool pool = new ForkJoinPool();

        System.out.println("\n--- ForkJoin Pool ---");

        RecursiveSumTask task = new RecursiveSumTask(1, 1000000);
        Integer result = pool.invoke(task);

        System.out.println("Parallel sum result: " + result);
        pool.shutdown();
    }

    public static class RecursiveSumTask extends RecursiveTask<Integer> {
        private final int start;
        private final int end;

        public RecursiveSumTask(int start, int end) {
            this.start = start;
            this.end = end;
        }

        @Override
        protected Integer compute() {
            if (end - start <= 10000) {
                // Compute directly
                int sum = 0;
                for (int i = start; i <= end; i++) {
                    sum += i;
                }
                return sum;
            } else {
                // Split task
                int mid = (start + end) / 2;
                RecursiveSumTask leftTask = new RecursiveSumTask(start, mid);
                RecursiveSumTask rightTask = new RecursiveSumTask(mid + 1, end);

                leftTask.fork();
                Integer rightResult = rightTask.compute();
                Integer leftResult = leftTask.join();

                return leftResult + rightResult;
            }
        }
    }
}

// 6. Async Tasks with Callback
class AsyncWithCallback {

    public interface AsyncCallback<T> {
        void onSuccess(T result);
        void onFailure(Exception e);
    }

    public void executeAsyncTask(final AsyncCallback<String> callback) {
        ExecutorService executor = Executors.newSingleThreadExecutor();

        executor.submit(new Callable<String>() {
            @Override
            public String call() throws Exception {
                // Simulate work
                Thread.sleep(1000);
                return "Task completed successfully";
            }
        }).addCallback(new AsyncCallback<String>() {
            @Override
            public void onSuccess(String result) {
                callback.onSuccess(result);
            }

            @Override
            public void onFailure(Exception e) {
                callback.onFailure(e);
            }
        });

        executor.shutdown();
    }

    // Helper method to add callback to Future
    private <T> Future<T> addCallback(final Future<T> future, final AsyncCallback<T> callback) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    T result = future.get();
                    callback.onSuccess(result);
                } catch (Exception e) {
                    callback.onFailure(e);
                }
            }
        }).start();

        return future;
    }
}

// 7. Thread Pool Monitoring
class ThreadPoolMonitoring {

    public void monitorThreadPool() {
        ThreadPoolExecutor executor = new ThreadPoolExecutor(
            2, 4, 60, TimeUnit.SECONDS,
            new LinkedBlockingQueue<Runnable>(10)
        );

        System.out.println("\n--- Thread Pool Monitoring ---");

        // Start monitoring thread
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (!executor.isTerminated()) {
                    System.out.println("Active: " + executor.getActiveCount() +
                                     ", Pool: " + executor.getPoolSize() +
                                     ", Queue: " + executor.getQueue().size() +
                                     ", Completed: " + executor.getCompletedTaskCount());
                    try {
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        break;
                    }
                }
            }
        }).start();

        // Submit some tasks
        for (int i = 0; i < 10; i++) {
            final int taskId = i;
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(1000);
                        System.out.println("Task " + taskId + " completed");
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            });
        }

        executor.shutdown();
        try {
            executor.awaitTermination(10, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

// Main demonstration
class ThreadPoolDemo {
    public static void demonstrateThreadPoolUsage() {
        System.out.println("=== Android Java Thread Pool Examples ===\n");

        // 1. ExecutorService pools
        ExecutorServicePools executorPools = new ExecutorServicePools();
        executorPools.fixedThreadPoolExample();

        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        executorPools.cachedThreadPoolExample();

        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        executorPools.singleThreadExecutorExample();

        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        executorPools.scheduledExecutorExample();

        // 2. Custom thread pool
        CustomThreadPoolExample customPool = new CustomThreadPoolExample();
        customPool.customThreadPoolExample();

        try {
            Thread.sleep(4000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 3. Future example
        System.out.println("\n--- Future Examples ---");
        FutureExample futureExample = new FutureExample();
        futureExample.submitWithFuture();

        try {
            Thread.sleep(4000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        futureExample.invokeAnyExample();

        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 4. Completion service
        CompletionServiceExample completionExample = new CompletionServiceExample();
        completionExample.completionServiceDemo();

        try {
            Thread.sleep(8000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 5. ForkJoin pool
        ForkJoinPoolExample forkJoinExample = new ForkJoinPoolExample();
        forkJoinExample.parallelSum();

        // 6. Thread pool monitoring
        ThreadPoolMonitoring monitoring = new ThreadPoolMonitoring();
        monitoring.monitorThreadPool();

        try {
            Thread.sleep(12000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println("\n=== All Thread Pool Examples Completed ===");
    }
}