ProducerConsumerDemo.java

// 5. PRODUCER-CONSUMER PROBLEM - Coordinating threads producing and consuming data
// Problem: Producer must wait if buffer is full, Consumer must wait if buffer is empty
public class ProducerConsumerDemo {
    static class Buffer {
        private final int[] buffer = new int[3]; // Limited buffer size
        private int count = 0; // Current items in buffer
        
        // Produce an item - wait if buffer is full
        public synchronized void produce(int value) throws InterruptedException {
            while (count == buffer.length) {
                System.out.println("Buffer FULL - Producer waiting...");
                wait(); // Wait for consumer to consume
            }
            buffer[count++] = value;
            System.out.println("Produced: " + value + " (Buffer size: " + count + "/" + buffer.length + ")");
            notifyAll(); // Notify consumer
        }
        
        // Consume an item - wait if buffer is empty
        public synchronized int consume() throws InterruptedException {
            while (count == 0) {
                System.out.println("Buffer EMPTY - Consumer waiting...");
                wait(); // Wait for producer to produce
            }
            int value = buffer[--count];
            System.out.println("Consumed: " + value + " (Buffer size: " + count + "/" + buffer.length + ")");
            notifyAll(); // Notify producer
            return value;
        }
    }

    public static void main(String[] args) {
        Buffer buffer = new Buffer();
        
        // Producer thread
        Thread producer = new Thread(() -> {
            try {
                for (int i = 1; i <= 5; i++) {
                    buffer.produce(i * 10);
                    Thread.sleep(500);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        
        // Consumer thread
        Thread consumer = new Thread(() -> {
            try {
                for (int i = 0; i < 5; i++) {
                    buffer.consume();
                    Thread.sleep(1000);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        
        producer.start();
        consumer.start();
    }
}