线程经典代码二,（同步情况下的生产者/消费者关系）

同步情况下的生产者/消费者关系 

//Buffer接口方法
public interface Buffer ...{

    public void set(int value);
    public int get();
}



//消费者
public class Consumer extends Thread...{

     private Buffer sharedLocation;

        public Consumer(Buffer shared)
        ...{
            super("Consumer");
            sharedLocation  = shared;
        }

        public void run()
        ...{
            int sum=0;
            for(int i=1;i<=4;i++)
            ...{
                try...{
                    Thread.sleep((int)(Math.random() * 3001));
                    sum = sum + sharedLocation.get();
                 }catch(InterruptedException e)...{
                    e.printStackTrace();
                }
            }

            System.err.println(getName() + "done producing." + " Termination" + getName() + ".");
        }

}



//生产者
public class Product extends Thread...{

     private Buffer sharedLocation;

        public Product(Buffer shared)
        ...{
            super("Product");
            sharedLocation  = shared;
        }

        public void run()
        ...{
            for(int i=1;i<=4;i++)
            ...{
                try...{
                    Thread.sleep((int)(Math.random() * 3001));
                    sharedLocation.set(i);
                }catch(InterruptedException e)...{
                    e.printStackTrace();
                }
            }

            System.err.println(getName() + "done producing." + " Termination" + getName() + ".");
        }

}



//实现对共享数据的同步访问方法
public class SynchronizedBuffer implements Buffer...{

    private int buffer = -1;
    private int occupiedBufferCount = 0;
    public synchronized void set(int value)
    ...{
        String name = Thread.currentThread().getName();
        
        while(occupiedBufferCount == 1)...{
            try...{
                System.err.println(name + " tries to write.");
                displayState( "Buffer full. " + name + "waits.");
                wait();
            }catch(InterruptedException e)...{
                e.printStackTrace();
            }
        }
        
        buffer = value;
        ++occupiedBufferCount;
        
        displayState(name + "writes" + buffer);
        notify();
    }
    
    public synchronized int get() ...{

        String name = Thread.currentThread().getName();
        while(occupiedBufferCount==0)...{
            
            try ...{
                System.err.println(name + "tries to read");
                displayState("Buffer empty." + name + "waits");
                wait();
            } catch (InterruptedException e) ...{
                // TODO 自动生成 catch 块
                e.printStackTrace();
            }
        }
        
        --occupiedBufferCount;
        displayState(name + "reads" + buffer);
        
        notify();
        
        return buffer;
    }

    
    public void displayState(String operation) ...{

        StringBuffer outputLine = new StringBuffer(operation);
        outputLine.setLength(40);
        outputLine.append(buffer + " " + occupiedBufferCount);
        System.err.println(outputLine);
        System.err.println();
        
    }


}



//测试类
public class SharedBufferTest2 ...{

    public static void main(String[] arg)...{
        SynchronizedBuffer sharedLocation = new SynchronizedBuffer();
        
        StringBuffer columnHeads = new StringBuffer("Operation");
        columnHeads.setLength(40);
        columnHeads.append("Buffer Occupied Count");
        System.err.println(columnHeads);
        System.err.println();
        sharedLocation.displayState("Initial State");
        
        Product product = new Product(sharedLocation);
        Consumer consumer = new Consumer(sharedLocation);
        
        product.start();
        consumer.start();
    }
}