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java中利用管程实现同步互斥量
其实我关于代码中信号量和管程的具体差别不是特别的清楚。 但是因为用到了Semaphore类（信号量），就是用信号量实现的。程序员们需要自己对信号量的初始化、更新（wait/signal）以及信号量更新逻辑负责。 而管程应该是用到了synchronized的定义方法，如public synchronized void insert(int val)，这个时候并不需要自己去实现信号量的等待、释放，只需要直接调用就行，
生产者消费者
import java.util.*;
public class ProduceConsume
{
static final int N = 2;//define the size of the buffer
static producer p = new producer();//initial a thread of producer
static consumer c = new consumer();//initial a thread of consumer
static our_monitor mon = new our_monitor();//initial a thread of a new pipe
public static void main(String args[])
{
p.start();
c.start();
}
static class producer extends Thread
{
public void run()
{
int item;
while(true) //the loop of a producer
{
item = produce_item();
mon.insert(item);
}
}
private int produce_item()
{
int p=1;
System.out.println("Produce:"+p);
return p;
}
}
static class consumer extends Thread
{
public void run()
{
int item;
while(true)
{
item = mon.remove();
consume_item(item);
}
}
private void consume_item(int item)
{
System.out.println("consumer:"+item);
}
}
static class our_monitor //a pipe
{
private int buffer[] = new int[N];
private int count = 0,lo = 0, hi = 0;
public synchronized void insert(int val)
{
try
{
Thread.sleep(500);
}
catch(InterruptedException e)
{
System.out.println("error");
}
if(count == N)go_to_sleep();
buffer[hi] = val;
hi=(hi + 1) % N;
count = count + 1;
if(count == 1)notify();
}
public synchronized int remove()
{
try
{
Thread.sleep(500);
}
catch(InterruptedException e)
{
System.out.println("error");
}
int val;
if(count == 0)go_to_sleep();
val = buffer[lo];
lo = (lo + 1) % N;
count = count -1;
if(count == N-1)notify();
return val;
}
private void go_to_sleep()
{
try
{
wait();
}
catch(InterruptedException e)
{
System.out.println("error");
}
}
}
}
读写问题
这是用信号量实现的。
import java.util.*;
import java.util.concurrent.Semaphore;
public class OS_Readerwriter
{
static Semaphore sem=new Semaphore(1);
static Semaphore sem_wrt=new Semaphore(1);
static int readercount=0;
static String a="hahaha";
public static void main(String args[])
{
class reader implements Runnable
{
public reader()
{
}
@Override
public void run()
{
// TODO Auto-generated method stub
try
{
sem.acquire();
readercount++;
}
catch (InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
if(readercount==1)
{
try
{
sem_wrt.acquire();
}
catch (InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
sem.release();
System.out.println("Reading "+a);
try
{
sem.acquire();
}
catch (InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
readercount--;
if(readercount==0)
{
sem_wrt.release();
}
sem.release();
}
}
class writer implements Runnable
{
public writer()
{
}
@Override
public void run()
{
// TODO Auto-generated method stub
try
{
sem_wrt.acquire();
}
catch (InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
a=a+"abc";
System.out.println("Writing "+a);
sem_wrt.release();
}
}
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