我遇到了一个问题,即每次程序填充阵列列表缓冲区中的所有位置时,程序都会停止执行。但是,从理论上讲。消费者流程仍然可以进入get()函数,导致Nockempty信号的信号值现在达到10个。因此,在消费者流程将信号值释放回信号eotfull之后,生产者过程仍然可以工作。
但它只是停止,我找不到问题。
这是程序:
import java.util.List;
import java.util.ArrayList;
import java.util.Random;
import java.util.concurrent.Semaphore;
/**
* A bounded buffer maintains a fixed number of "slots". Items can be
* inserted into and removed from the buffer. The buffer has a maximum
* size.
*/
class BoundedBuffer2
{
// the maximum size of the bounded buffer
final public static int MAXSIZE = 10;
Semaphore notEmpty = new Semaphore(0);
Semaphore notFull = new Semaphore(MAXSIZE);
Semaphore sema = new Semaphore(1);
// the buffer
volatile List<Integer> buffer;
public BoundedBuffer2()
{
buffer = new ArrayList<Integer>();
}
// add an element to the end of the buffer if it is not full
public synchronized void put(int input)
throws InterruptedException
{
notFull.acquire();
sema.acquire();
buffer.add(input);
sema.release();
notEmpty.release();
}
// take an element from the front of the buffer
public synchronized int get()
throws InterruptedException
{
notEmpty.acquire();
sema.acquire();
int result = buffer.remove(0);
sema.release();
notFull.release();
return result;
}
public int size()
{
int result = buffer.size();
return result;
}
}
/**
* An instance of the Producer class produces new integers at random
* intervals, and inserts them into a bounded buffer.
*/
class Producer2 extends Thread
{
// the buffer in which to insert new integers
BoundedBuffer2 buffer;
public Producer2(BoundedBuffer2 buffer)
{
this.buffer = buffer;
}
public void run()
{
Random random = new Random();
try {
while (true) {
Thread.sleep(100);
//insert a random integer
int next = random.nextInt();
buffer.put(next);
System.err.println("b.size() increases to " + buffer.size());
}
}
catch (InterruptedException e) {}
}
}
/**
* An instance of the Consumer class consumes integers from a bounded
* buffer at random intervals.
*/
class Consumer2 extends Thread
{
// the buffer in which to insert new integers
BoundedBuffer2 buffer;
public Consumer2(BoundedBuffer2 buffer)
{
this.buffer = buffer;
}
public void run()
{
Random random = new Random();
try {
while (true) {
Thread.sleep(200);
//get the next integer from the buffer
int next = buffer.get();
System.err.println("next = " + next);
System.err.println("b.size() reducted to " + buffer.size());
}
}
catch (InterruptedException e) {}
}
}
public class UseBuffer2
{
public static void main(String [] args)
{
BoundedBuffer2 buffer = new BoundedBuffer2();
Producer2 p = new Producer2(buffer);
Consumer2 c = new Consumer2(buffer);
p.start();
c.start();
}
}
这是控制台的输出:
b.size() increases to 1
b.size() increases to 2
next = 400524264
b.size() reducted to 1
b.size() increases to 2
b.size() increases to 3
next = 241523118
b.size() reducted to 2
b.size() increases to 3
next = -1618289090
b.size() reducted to 2
b.size() increases to 3
b.size() increases to 4
next = -316455080
b.size() reducted to 3
b.size() increases to 4
b.size() increases to 5
next = 338682909
b.size() reducted to 4
b.size() increases to 5
b.size() increases to 6
next = -961276708
b.size() reducted to 5
b.size() increases to 6
b.size() increases to 7
next = 2056804692
b.size() reducted to 6
b.size() increases to 7
b.size() increases to 8
next = -301063524
b.size() reducted to 7
b.size() increases to 8
b.size() increases to 9
next = -148582342
b.size() reducted to 8
b.size() increases to 9
b.size() increases to 10
next = -2076430410
b.size() reducted to 9
b.size() increases to 10
阅读同步关键字的工作方式:https://docs.oracle.com/javase/javase/tutorial/essential/essention/concurrency/concurrency/syncmeth.html
相关部分:
不可能在同步方法上进行两种调用 相同的对象交织在一起。当一个线程执行同步时 对象的方法,所有调用同步的其他线程 同一对象块的方法(暂停执行),直到第一个 线程是用对象完成的。
您的put()
和get()
方法已同步。因此,如果生产者进入put()
方法,请尝试获取notFull
信号量,但不能因为缓冲区已满,它会永远阻止,并在输入同步方法时保持其获得的锁定。因此,消费者无法输入get()方法,也无法从缓冲区中删除元素。