ReentrantLock Example code

ReentrantLockApp.java

package appstart.mymodappdemo;

import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.Condition;

public class ReentrantLockApp {

    public static void main(String[] args) {

        Store store = new Store();
        Producer producer = new Producer(store);
        Consumer consumer = new Consumer(store);
        new Thread(producer).start();
        new Thread(consumer).start();
    }
}

// Класс Магазин, хранящий произведенные товары
class Store {
    ReentrantLock locker;
    Condition condition;
    private int product = 0;

    Store() {
        locker = new ReentrantLock(); // creating lock
        condition = locker.newCondition(); // get condition related to the lock
    }

    public void get() {

        locker.lock();
        try {
// waiting for the goods (products) to appear in the store 
            while (product < 1)
                condition.await();

            product--;
            System.out.println("Buyer bought 1 item");
            System.out.println("Goods in stock: " + product);

// signal to all threads that awaiting that they can continue
            condition.signalAll();
        } catch (InterruptedException e) {
            System.out.println(e.getMessage());
        } finally {
            locker.unlock();
        }
    }

    public void put() {

        locker.lock();
        try {
// we can store only three product items in the store
            while (product >= 3)
                condition.await();

            product++;
            System.out.println("Producer added 1 item");
            System.out.println("Goods in stock: " + product);
            
// signal to all threads that awaiting that they can continue
            condition.signalAll();
        } catch (InterruptedException e) {
            System.out.println(e.getMessage());
        } finally {
            locker.unlock();
        }
    }
}

class Producer implements Runnable {

    Store store;

    Producer(Store store) {
        this.store = store;
    }

    public void run() {
        for (int i = 1; i < 6; i++) {
            store.put();
        }
    }
}

class Consumer implements Runnable {

    Store store;

    Consumer(Store store) {
        this.store = store;
    }

    public void run() {
        for (int i = 1; i < 6; i++) {
            store.get();
        }
    }
}