

package cn.xf.cp.ch14;

/**
 * 
 *功能：有界緩存實(shí)現(xiàn)基類
 *時(shí)間：下午2:20:00
 *文件：BaseBoundedBuffer.java 
 *@author Administrator
 *
 * @param <V>
 */
public class BaseBoundedBuffer<V>
{
  private final V[] buf;
  private int tail;
  private int head;
  private int count;
  
  public BaseBoundedBuffer(int capacity)
  {
    //初始化數(shù)組
    this.buf = (V[]) new Object[capacity];
  }
  
  //放入一個(gè)數(shù)據(jù),final方法無法被重寫
  protected synchronized final void doPut(V v)
  {
    buf[tail] = v;
    if(++tail == buf.length)
    {
      tail = 0;
    }
    //插入一個(gè)方法，總量++
    ++count;
  }
  
  /**
   * 取出一個(gè)數(shù)據(jù)
   * @return
   */
  protected synchronized final V doTake()
  {
    V v = buf[head];
    buf[head] = null;
    if(++head == buf.length)
    {
      head = 0;
    }
    --count;
    return v;
  }
  
  //通過對(duì)count的判斷，來確定數(shù)組是否是滿的
  public synchronized final boolean isFull()
  {
    return count == buf.length;
  }
  
  public synchronized final boolean isEmpty()
  {
    return count == 0;
  }
}

2、判定前提條件再執(zhí)行操作



package cn.xf.cp.ch14;

/**
 * 
 *功能：對(duì)插入和獲取元素操作進(jìn)行先行檢查，然后執(zhí)行操作，校驗(yàn)不通過不予操作
 *時(shí)間：下午2:33:41
 *文件：GrumpyBoundedBuffer.java 
 *@author Administrator
 *
 * @param <V>
 */
public class GrumpyBoundedBuffer<V> extends BaseBoundedBuffer<V>
{

  public GrumpyBoundedBuffer(int size)
  {
    super(size);
  }
  
  public synchronized void put(V v) throws Exception
  {
    //如果是滿的隊(duì)列，就無法插入新的元素
    if(this.isFull())
    {
      throw new Exception("隊(duì)列超出");
    }
    this.doPut(v);
  }
  
  //同理，隊(duì)列為空的就無法取出新的元素
  public synchronized V take() throws Exception
  {
    if(this.isEmpty())
    {
      throw new Exception("隊(duì)列中無元素");
    }
    
    return this.doTake();
  }

}

3、通過輪詢與休眠來實(shí)現(xiàn)簡(jiǎn)單的阻塞



package cn.xf.cp.ch14;

/**
 * 
 *功能：通過輪詢與休眠來實(shí)現(xiàn)簡(jiǎn)單的阻塞
 *時(shí)間：下午2:55:54
 *文件：SleepyBoundedBuffer.java 
 *@author Administrator
 *
 * @param <V>
 */
public class SleepyBoundedBuffer<V> extends BaseBoundedBuffer<V>
{
  //2s
  private static final long SLEEP_GRANULARITY = 2000;

  public SleepyBoundedBuffer(int capacity)
  {
    super(capacity);
  }
  
  //放入隊(duì)列的時(shí)候
  public void put(V v) throws InterruptedException
  {
    while(true)
    {
      //這里不對(duì)循環(huán)上鎖，不然這個(gè)鎖就無法釋放了，不對(duì)休眠上鎖，休眠上鎖，在休眠的時(shí)候別人也無法操作，永遠(yuǎn)都不可能有元素出去
      synchronized (this)
      {
        //如果隊(duì)列不是滿的，那么就放入元素
        if(!this.isFull())
        {
          this.doPut(v);
          return;
        }
      }
      //否則休眠，退出cpu占用
      Thread.sleep(SLEEP_GRANULARITY);
    }
  }
  
  public V take() throws InterruptedException
  {
    while(true)
    {
      //這里不對(duì)循環(huán)上鎖，不然這個(gè)鎖就無法釋放了，不對(duì)休眠上鎖，休眠上鎖，在休眠的時(shí)候別人也無法操作，永遠(yuǎn)都不可能有新的元素進(jìn)來
      synchronized(this)
      {
        //如果數(shù)組部位空，那么就可以取出數(shù)據(jù)
        if(!this.isEmpty())
        {
          return this.doTake();
        }
        //如果隊(duì)列為空，休眠幾秒再試
      }
      Thread.sleep(SLEEP_GRANULARITY);
    }
  }
  
}

4、條件隊(duì)列



package cn.xf.cp.ch14;

/**
 * 
 *功能：使用條件隊(duì)列
 *時(shí)間：下午3:32:04
 *文件：BoundedBuffer.java 
 *@author Administrator
 *
 * @param <V>
 */
public class BoundedBuffer<V> extends BaseBoundedBuffer<V>
{

  public BoundedBuffer(int capacity)
  {
    super(capacity);
  }
  
  /**
   * 放入數(shù)據(jù)元素
   * @param v
   * @throws InterruptedException
   */
  public synchronized void put(V v) throws InterruptedException
  {
    while(this.isFull())
    {
      //這里掛起程序，會(huì)釋放鎖
      this.wait();
    }
    //如果隊(duì)列不為滿的，那么程序被喚醒之后從新獲取鎖
    this.doPut(v);
    //執(zhí)行結(jié)束，喚醒其他隊(duì)列
    this.notifyAll();
  }
  
  public synchronized V take() throws InterruptedException
  {
    while(this.isEmpty())
    {
      this.wait();
    }
    V v = this.doTake();
    this.notifyAll();
    return v;
  }
  
}

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