我已经使用可重入锁和条件编写了生产者消费者程序。它工作正常，但是我不确定实施是否正确。而且，它似乎不是最佳的。可以请人确认这是否是正确的实现，还可以请您说一下如何优化它，例如-在真正需要的地方锁定
public class TestRL {
static class Observed {
boolean filled = false;
public void setFilled(boolean filled) {
this.filled = filled;
}
public boolean getFilled() {
return filled;
}
}
static Observed observed = new Observed();
static class Consumer implements Runnable {
Observed observed;
ReentrantLock lock;
Condition condition;
Consumer(Observed observed, ReentrantLock lock, Condition condition) {
this.observed = observed;
this.lock = lock;
this.condition = condition;
}
@Override
public void run() {
lock.lock();
try {
for (int i = 0; i < 20; i++) {
if (observed.getFilled() == false) {
try {
System.out.println("consumer waiting");
condition.await();
System.out.println("consumed");
Thread.sleep(400 + 1000 * i % 2);
} catch (InterruptedException e1) {
e1.printStackTrace();
}
observed.setFilled(false);
condition.signalAll();
}else{
observed.setFilled(false);
condition.signalAll();
}
}
} finally {
lock.unlock();
}
}
}
static class Producer implements Runnable {
Observed observed;
ReentrantLock lock;
Condition condition;
Producer(Observed observed, ReentrantLock lock, Condition condition) {
this.observed = observed;
this.lock = lock;
this.condition = condition;
}
@Override
public void run() {
lock.lock();
try {
for (int i = 0; i < 20; i++) {
if (observed.getFilled() == true) {
try {
System.out.println("producer waiting");
condition.await();
System.out.println("produced");
Thread.sleep(1000);
} catch (InterruptedException e1) {
e1.printStackTrace();
}
observed.setFilled(true);
condition.signalAll();
}else{
observed.setFilled(true);
condition.signalAll();
}
}
} finally {
lock.unlock();
}
}
}
/**
* @param args
*/
public static void main(String[] args) {
ReentrantLock lock = new ReentrantLock();
Condition condition = lock.newCondition();
Producer producer = new Producer(observed, lock, condition);
Consumer consumer = new Consumer(observed, lock, condition);
Thread t1 = new Thread(producer);
Thread t2 = new Thread(consumer);
t1.start();
t2.start();
}
}
最佳答案
以下是使用ReentrantLock＆Condition解决生产者－消费者问题的另一个示例代码。以防万一有人要。
package reentrant_prodcons;
import java.util.LinkedList;
import java.util.Queue;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Reentrant_ProdCons {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
Queue<Integer> queue=new LinkedList<Integer>();
ReentrantLock lock=new ReentrantLock();
Condition con=lock.newCondition();
final int size = 5;
new Producer(lock, con, queue, size).start();
new Consumer(lock, con, queue).start();
}
}
class Producer extends Thread{
ReentrantLock lock;
Condition con;
Queue<Integer> queue;
int size;
public Producer(ReentrantLock lock, Condition con, Queue<Integer> queue, int size) {
this.lock = lock;
this.con = con;
this.queue = queue;
this.size=size;
}
public void run(){
for(int i=0;i<10;i++){
lock.lock();
while(queue.size()==size){
try {
con.await();
} catch (InterruptedException ex) {
Logger.getLogger(Producer.class.getName()).log(Level.SEVERE, null, ex);
}
}
queue.add(i);
System.out.println("Produced : "+i);
con.signal();
lock.unlock();
}
}
}
class Consumer extends Thread{
ReentrantLock lock;
Condition con;
Queue<Integer> queue;
public Consumer(ReentrantLock lock, Condition con, Queue<Integer> queue) {
this.lock = lock;
this.con = con;
this.queue = queue;
}
public void run(){
for(int i=0;i<10;i++){
lock.lock();
while(queue.size()<1){
try {
con.await();
} catch (InterruptedException ex) {
Logger.getLogger(Consumer.class.getName()).log(Level.SEVERE, null, ex);
}
}
System.out.println("Consumed : "+queue.remove());
con.signal();
lock.unlock();
}
}
}