Condition 與 Object 在通信上的對比
阿新 • • 發佈:2017-10-30
== 消費者模式 ble 喚醒 on() @override 多個 ons current
Condition 將 Object的通信方法(wait、notify 和 notifyAll)分解成截然不同的對象,用await()替換wait(),用signal()替換notify(),用signalAll()替換notifyAll(),傳統線程的通信方式,Condition都可以實現,這裏註意,Condition是被綁定到Lock上的,要創建一個Lock的Condition必須用newCondition()方法。
Condition的強大之處在於它可以為多個線程間建立不同的Condition, 使用synchronized/wait()只有一個阻塞隊列,notifyAll會喚起所有阻塞隊列下的線程,而使用lock/condition,可以實現多個阻塞隊列,signalAll只會喚起某個阻塞隊列下的阻塞線程。
- 使用synchronized/wait()實現生產者消費者模式如下:
//模擬生產和消費的對象
class Buffer {
private int maxSize;
private List<Date> storage;
Buffer(int size){
maxSize=size;
storage=new LinkedList<>();
}
//生產方法
public synchronized void put() {
try {
while (storage.size() ==maxSize ){//如果隊列滿了
System.out.print(Thread.currentThread().getName()+": wait \n");;
wait();//阻塞線程
}
storage.add(new Date());
System.out.print(Thread.currentThread().getName()+": put:"+storage.size()+ "\n");
Thread.sleep(1000);
notifyAll();//喚起線程
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//消費方法
public synchronized void take() {
try {
while (storage.size() ==0 ){//如果隊列滿了
System.out.print(Thread.currentThread().getName()+": wait \n");;
wait();//阻塞線程
}
Date d=((LinkedList<Date>)storage).poll();
System.out.print(Thread.currentThread().getName()+": take:"+storage.size()+ "\n");
Thread.sleep(1000);
notifyAll();//喚起線程
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
//生產者
class Producer implements Runnable{
private Buffer buffer;
Producer(Buffer b){
buffer=b;
}
@Override
public void run() {
while(true){
buffer.put();
}
}
}
//消費者
class Consumer implements Runnable{
private Buffer buffer;
Consumer(Buffer b){
buffer=b;
}
@Override
public void run() {
while(true){
buffer.take();
}
}
}
//
public class Main{
public static void main(String[] arg){
Buffer buffer=new Buffer(10);
Producer producer=new Producer(buffer);
Consumer consumer=new Consumer(buffer);
//創建線程執行生產和消費
for(int i=0;i<3;i++){
new Thread(producer,"producer-"+i).start();
}
for(int i=0;i<3;i++){
new Thread(consumer,"consumer-"+i).start();
}
}
}
- 使用lock/condition實現生產者消費者模式如下:
import java.util.Date;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
class Buffer {
private final Lock lock;
private final Condition notFull;
private final Condition notEmpty;
private int maxSize;
private List<Date> storage;
Buffer(int size){
//使用鎖lock,並且創建兩個condition,相當於兩個阻塞隊列
lock=new ReentrantLock();
notFull=lock.newCondition();
notEmpty=lock.newCondition();
maxSize=size;
storage=new LinkedList<>();
}
public void put() {
lock.lock();
try {
while (storage.size() ==maxSize ){//如果隊列滿了
System.out.print(Thread.currentThread().getName()+": wait \n");;
notFull.await();//阻塞生產線程
}
storage.add(new Date());
System.out.print(Thread.currentThread().getName()+": put:"+storage.size()+ "\n");
Thread.sleep(1000);
notEmpty.signalAll();//喚醒消費線程
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
lock.unlock();
}
}
public void take() {
lock.lock();
try {
while (storage.size() ==0 ){//如果隊列滿了
System.out.print(Thread.currentThread().getName()+": wait \n");;
notEmpty.await();//阻塞消費線程
}
Date d=((LinkedList<Date>)storage).poll();
System.out.print(Thread.currentThread().getName()+": take:"+storage.size()+ "\n");
Thread.sleep(1000);
notFull.signalAll();//喚醒生產線程
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
lock.unlock();
}
}
}
class Producer implements Runnable{
private Buffer buffer;
Producer(Buffer b){
buffer=b;
}
@Override
public void run() {
while(true){
buffer.put();
}
}
}
class Consumer implements Runnable{
private Buffer buffer;
Consumer(Buffer b){
buffer=b;
}
@Override
public void run() {
while(true){
buffer.take();
}
}
}
public class Main{
public static void main(String[] arg){
Buffer buffer=new Buffer(10);
Producer producer=new Producer(buffer);
Consumer consumer=new Consumer(buffer);
for(int i=0;i<3;i++){
new Thread(producer,"producer-"+i).start();
}
for(int i=0;i<3;i++){
new Thread(consumer,"consumer-"+i).start();
}
}
}
Condition 與 Object 在通信上的對比