经典笔试题：写一个固定容量的同步容器

写一个固定容量的同步容器，拥有put和get方法，以及getCount方法，能够支持2个生产者线程以及10个消费者线程的阻塞调用

 第一种写法：

/**
 * 面试题：写一个固定容量同步容器，拥有put和get方法，以及getCount方法，
 * 能够支持2个生产者线程以及10个消费者线程的阻塞调用
 * 
 * 使用wait和notify/notifyAll来实现
 * 
 */
import java.util.LinkedList;
import java.util.concurrent.TimeUnit;

public class MyContainer1<T> {

    final private LinkedList<T> lists = new LinkedList<T>();
    final private int MAX = 10; // 最多10个元素
    private int count = 0;

    public synchronized void put(T t) {
        while (lists.size() == MAX) {
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        lists.add(t);
        count++;
        this.notifyAll();// 通知消费者线程进行消费
    }

    public synchronized T get() {
        T t = null;
        while (lists.size() == 0) {
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        t = lists.removeFirst();
        count--;
        this.notifyAll(); // 通知生产者进行生产
        return t;
    }

    public static void main(String[] args) {
        MyContainer1<String> c = new MyContainer1<>();
        // 启动消费者线程
        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                for (int j = 0; j < 5; j++) {
                    System.out.println("消费" + c.get());
                }
            }, "c" + i).start();
        }

        try {
            TimeUnit.SECONDS.sleep(2);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 启动生产者线程
        for (int i = 0; i < 2; i++) {
            new Thread(() -> {
                for (int j = 0; j < 25; j++) {
                    System.out.println("生产" + Thread.currentThread().getName() + " " + j);
                    c.put(Thread.currentThread().getName() + " " + j);
                }
            }, "p" + i).start();
        }
    }
}

 

第二种写法：

/**
 * 面试题：写一个固定容量同步容器，拥有put和get方法，以及getCount方法， 能够支持2个生产者线程以及10个消费者线程的阻塞调用
 * 
 * 使用Lock和Condition来实现 对比两种方式，Condition的方式可以更加精确的指定哪些线程被唤醒
 * 
 */
import java.util.LinkedList;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class MyContainer2<T> {

    final private LinkedList<T> list = new LinkedList<T>();
    final private int MAX = 10; // 最多10个元素
    private int count = 0;

    private Lock lock = new ReentrantLock();
    private Condition producer = lock.newCondition();
    private Condition consumer = lock.newCondition();

    public void put(T t) {
        try {
            lock.lock();
            while (list.size() == MAX) {
                producer.await();
            }
            list.add(t);
            count++;
            consumer.signalAll();// 通知消费者线程进行消费
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public T get() {
        T t = null;
        try {
            lock.lock();
            while (list.size() == 0) {
                consumer.await();
            }
            t = list.removeFirst();
            count--;
            producer.signalAll(); // 通知生产者进行生产
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.lock();
        }
        return t;
    }

    public static void main(String[] args) {
        MyContainer2<String> c = new MyContainer2<>();
        // 启动消费者线程
        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                for (int j = 0; j < 5; j++) {
                    System.out.println("消费" + c.get());
                }
            }, "c" + i).start();
        }

        try {
            TimeUnit.SECONDS.sleep(2);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // 启动生产者线程
        for (int i = 0; i < 2; i++) {
            new Thread(() -> {
                for (int j = 0; j < 25; j++) {
                    System.out.println("生产" + Thread.currentThread().getName() + " " + j);
                    c.put(Thread.currentThread().getName() + " " + j);
                }
            }, "p" + i).start();
        }
    }
}