认识达内从这里开始

缓存队列

package cn.study.concurrency.ch12;

import java.util.concurrent.Semaphore;

public class BoundedBuffer<E> {

//信号量

private final Semaphore availableItems, availableSpaces;

private final E[] items;

private int putPosition=0, takePosition=0;

public BoundedBuffer(int capacity)

{

availableItems = new Semaphore(0);

availableSpaces = new Semaphore(capacity);

items = (E[]) new Object[capacity];

}

public boolean isEmpty()

{

//这个表示已经是空的了

return availableItems.availablePermits() == 0;

}

public boolean isFull()

{

//表明这个是满的队列

return availableSpaces.availablePermits() == 0;

}

//放入一个对象，首先向availableSpaces请求一个信号量，然后结束之后返回一个availableItems信号

public void put(E x) throws InterruptedException

{

//减少一个许可

availableSpaces.acquire();

doInsert(x);

//添加一个许可

availableItems.release();

}

//释放一个数据对象

public E take() throws InterruptedException

{

//当释放一个对象的时候，减少一个连接许可

availableItems.acquire();

E item = doExtract();

availableSpaces.release();//取出数据之后，吧能插入的可能添加一个

return item;

}

private synchronized void doInsert(E x)

{

int i = putPosition;

items[i] = x;

putPosition = (++i == items.length) ? 0 : i;

}

//不论是取数据，还是获取数据，都是循环取得

private synchronized E doExtract()

{

int i = takePosition;

E x = items[i];

items[i] = null;

takePosition = (++i == items.length) ? 0: i;

return x;

}

public static void main(String[] args) throws InterruptedException {

BoundedBuffer<Integer> bb = new BoundedBuffer<Integer>(10);

bb.take();

if(bb.isEmpty())

{

System.out.println("空");

}

if(bb.isFull())

{

System.out.println("满");

}

}

}

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