1 package cn.sp.test; 2  3 import java.util.concurrent.Semaphore; 4  5 /** 6  * 有界的缓存 7  * @author pc 8  * 9  * @param 
     
      10  */11 public class BoundedBuffer
      
        {12     private final Semaphore availableItems;//可用项   信号量 13     private final Semaphore availableSpaces;//可用空间  信号量 14     private final E[] items;15     private  int putPosition = 0,takePosition = 0;16     17     @SuppressWarnings("unchecked")18     public BoundedBuffer(int capacity){19         availableItems = new Semaphore(0);20         availableSpaces = new Semaphore(capacity);21         items = (E[]) new Object[capacity];22     }23     24     public boolean isEmpty(){
   //可用许可为025         return availableItems.availablePermits() == 0;26     }27     28     public  boolean isFull(){
   //满时可用空间为029         return availableSpaces.availablePermits() == 0 ;30     }31     32     public void put(E x) throws InterruptedException{33         availableSpaces.acquire();34         doInsert(x);35         availableItems.release();36     }37     38     public E take() throws InterruptedException{39         availableItems.acquire();//从 availableItems 获取 一个许可40         E e = doExtract();41         availableSpaces.release();//返回  一个许可 到 availableSpaces42         return e;43     }44 45     private synchronized E doExtract() {46         int i = takePosition;47         E x = items[i];48         //取出后 调用垃圾收集器49         items[i] = null;50         takePosition = (++i == items.length)? 0 : i;51         return x;52     }53 54     private  synchronized void doInsert(E x) {
   //同步方法55         int i = putPosition;56         items[i] = x;57         //如果满了重置为058         putPosition = (++i == items.length) ? 0 :i;59         60     }61 }
      
     

测试类：

1 package cn.sp.test; 2  3 import org.junit.Assert; 4  5 public class Test { 6      7     public void test01(){ 8         BoundedBuffer
     
       boundedBuffer = new BoundedBuffer
      
       (10); 9         Assert.assertTrue(boundedBuffer.isEmpty());10         Assert.assertFalse(boundedBuffer.isFull());11     }12     @org.junit.Test13     public void test02() throws InterruptedException{14         BoundedBuffer
       
         boundedBuffer = new BoundedBuffer
        
         (10);15         16         for(int i=0;i<10;i++){17             boundedBuffer.put(i);18         }19         Assert.assertTrue(boundedBuffer.isFull());20         Assert.assertFalse(boundedBuffer.isEmpty());21         System.out.println(boundedBuffer.isFull());22     }23 }