java基础-手写ArrayBlockingQueue

-##### ArrayBlockingQueue

package com.byedbl.queue;
import java.io.Serializable;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

public class MyArrayBlockingQueue<E> implements Serializable {
    private static final long serialVersionUID = 102615140181641502L;

    private final E[] items;

    private int takeIndex;

    /** items index for next put, offer, or add. */
    private int putIndex;

    private final ReentrantLock lock;

    /** Condition for waiting takes */
    private final Condition notEmpty;
    /** Condition for waiting puts */
    private final Condition notFull;

    private int count;

    public MyArrayBlockingQueue(int capacity) {
        if (capacity <= 0)
            throw new IllegalArgumentException();
        this.items = (E[]) new Object[capacity];
        lock = new ReentrantLock();
        notEmpty = lock.newCondition();
        notFull = lock.newCondition();
    }

    public boolean add(E e) {
        if (offer(e)) {
            return true;
        } else {
            throw new IllegalStateException("Queue full");
        }
    }

    public boolean offer(E e) {
        if (e == null)
            throw new NullPointerException();
        lock.lock();
        try {
            if (count == items.length)
                return false;
            else {
                insert(e);
                return true;
            }
        } finally {
            lock.unlock();
        }
    }

    // 循环增加
    private final int inc(int i) {
        return (++i == items.length) ? 0 : i;
    }

    private void insert(E e) {
        items[putIndex] = e;
        putIndex = inc(putIndex);
        ++count;
        // 唤醒非空线程
        notEmpty.signal();
    }

    private E extract() {
        final E[] items = this.items;
        E e = items[takeIndex];
        items[takeIndex] = null;
        takeIndex = inc(takeIndex);
        --count;
        notFull.signal();
        return e;
    }

    public boolean offer(E e, long timeout, TimeUnit unit)
            throws InterruptedException {
        if (e == null)
            throw new NullPointerException();
        long nanos = unit.toNanos(timeout);
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            for (;;) {
                // 添加新元素
                if (count != items.length) {
                    insert(e);
                    return true;
                }
                // 没时间了就返回false
                if (nanos <= 0) {
                    return false;
                }
                // 等待
                try {
                    // 返回的nanos值会减去传入的nanos值,所以基本等一次就会为<=0了
                    nanos = notFull.awaitNanos(nanos);
                } catch (InterruptedException e1) {
                    notFull.signal();
                    throw e1;
                }
            }
        } finally {
            lock.unlock();
        }
    }

    public void put(E e) throws InterruptedException {
        if (e == null)
            throw new NullPointerException();
        final E[] items = this.items;
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            try {
                while (count == items.length) {
                    notFull.await();
                }
            } catch (InterruptedException e1) {
                notFull.signal();
                throw e1;
            }
            insert(e);
        } finally {
            lock.unlock();
        }
    }

    public E take() throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            try {
                while (count == 0) {
                    notEmpty.await();
                }
            } catch (InterruptedException e1) {
                notEmpty.signal();
                throw e1;
            }
            E e = extract();
            return e;
        } finally {
            lock.unlock();
        }
    }

    public E poll() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            if (count == 0) {
                return null;
            }
            return extract();
        } finally {
            lock.unlock();
        }
    }

    public E poll(long timeout, TimeUnit unit) throws InterruptedException {
        long nanos = unit.toNanos(timeout);
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            for (;;) {
                if (count == 0) {
                    try {
                        nanos = notEmpty.awaitNanos(nanos);
                    } catch (InterruptedException e) {
                        notEmpty.signal();
                        throw e;
                    }
                }
                if (nanos <= 0) {
                    return null;
                }
                return extract();
            }
        } finally {
            lock.unlock();
        }
    }

    public E peek() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return (count == 0) ? null : items[takeIndex];
        } finally {
            lock.unlock();
        }
    }

    public int size() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return count;
        } finally {
            lock.unlock();
        }
    }

    public boolean remove(E e) {
        if (e == null)
            throw new NullPointerException();
        final E[] items = this.items;
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            int i = takeIndex;
            int k = 0;
            for (;;) {
                if (k++ >= count)
                    return false;
                if (e.equals(items[i])) {
                    removeAt(i);
                    return true;
                }
                i = inc(i);
            }
        } finally {
            lock.unlock();
        }
    }

    private void removeAt(int i) {
        final E[] items = this.items;
        if(i == takeIndex){
            items[takeIndex] = null;
            takeIndex = inc(takeIndex);
        }else{
            for(;;){
                int nexti = inc(i);
                if(nexti != putIndex){
                    items[i] = items[nexti];
                    i = nexti;
                }else{
                    items[i] = null;
                    putIndex = i;
                    break;
                }
            }
        }
        --count;
        notFull.signal();
        
    }
    
    public boolean contains(Object o) {
        if (o == null) return false;
        final E[] items = this.items;
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            int i = takeIndex;
            int k = 0;
            while (k++ < count) {
                if (o.equals(items[i]))
                    return true;
                i = inc(i);
            }
            return false;
        } finally {
            lock.unlock();
        }
    }
    public String toString() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return super.toString();
        } finally {
            lock.unlock();
        }
    }
    
}

  • 测试

package com.byedbl.queue;

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

public class MyArrayBlockingQueueTest {

    public static void main(String[] args) throws InterruptedException {
        final ReentrantLock lock = new ReentrantLock();
        final Condition producer = lock.newCondition();
        final Condition consumer = lock.newCondition();

        final MyArrayBlockingQueue<Integer> queue = new MyArrayBlockingQueue<Integer>(2);
        // for(int i=0;i<6;i++){
        // queue.add(i);
        // }

        for (int i = 0; i < 2; i++) {
            queue.add(i);
        }

        
        Thread c = new Thread(new Runnable() {
            
            @Override
            public void run() {
                for(;;){
                    lock.lock();
                    try{
                        if(queue.size()>0){
                            Integer value = queue.poll();
                            System.out.println("poll a value:"+value);
                            producer.signal();
                            try {
                                consumer.await();
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                            
                        }
                    }finally{
                        lock.unlock();
                    }
                }
                
                
            }
        });
        c.start();

        Thread p = new Thread(new Runnable() {

            @Override
            public void run() {
                for(;;){
                    int value = new Random().nextInt(100);
                    lock.lock();
                    try{
                        if (!queue.contains(value)) {
                            queue.add(value);
                            System.out.println("add a value:"+value);
                            consumer.signal();
                            try {
                                producer.await();
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                            
                        }
                    }finally{
                        lock.unlock();
                    }
                        
                }
                
            }
        });
        
        p.start();
        Thread.sleep(50000);
        System.out.println(queue.size());
        System.out.println(queue.toString());
    }
}

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