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java之wait()、notify()實(shí)現(xiàn)非阻塞的生產(chǎn)者和消費(fèi)者
一、對(duì)于wait()和notify()的解釋
void notify()
Wakes up a single thread that is waiting on this object’s monitor.
喚醒等待獲取鎖資源的單個(gè)線程
void notifyAll()
Wakes up all threads that are waiting on this object’s monitor.
喚醒等待獲取鎖資源的所有線程
void wait( )
Causes the current thread to wait until another thread invokes the notify() method or the notifyAll( ) method for this object.
釋放出對(duì)象的鎖資源，程序會(huì)阻塞在這里
二、使用wait()、notify()、notifyAll()應(yīng)該要注意的地方
1、wait( )，notify( )，notifyAll( )都不屬于Thread類(lèi)，屬于Object基礎(chǔ)類(lèi)，每個(gè)對(duì)象都有wait( )，notify( )，notifyAll( ) 的功能，因?yàn)槊總€(gè)對(duì)象都有鎖
2、當(dāng)需要調(diào)用wait( )，notify( )，notifyAll( )的時(shí)候，一定都要在synchronized里面，不然會(huì)報(bào) IllegalMonitorStateException 異常，可以這樣理解，在synchronized(object) {}里面的代碼才能獲取到對(duì)象的鎖。
3、while循環(huán)里而不是if語(yǔ)句下使用wait，這樣，會(huì)在線程暫?；謴?fù)后都檢查wait的條件，并在條件實(shí)際上并未改變的情況下處理喚醒通知
4、調(diào)用obj.wait( )釋放了obj的鎖，程序就會(huì)阻塞在這里，如果后面被notify()或者notifyAll()方法呼喚醒了之后，那么程序會(huì)接著調(diào)用obj.wait()后面的程序。
5、notify()喚醒等待獲取鎖資源的單個(gè)線程，notifyAll( )喚醒等待獲取鎖資源的所有線程
6、當(dāng)調(diào)用obj.notify/notifyAll后，調(diào)用線程依舊持有obj鎖，其它線程仍無(wú)法獲得obj鎖，直到調(diào)用線程退出synchronized塊或者在原有的obj調(diào)用wait釋放鎖，其它的線程才能起來(lái)
三、使用wait()、notify()、notifyAll()實(shí)現(xiàn)非阻塞式的消費(fèi)者和生產(chǎn)者
package wait;
import java.util.PriorityQueue;
public class WaitAndNofityTest {
public static final int COUNT = 5;
//優(yōu)先隊(duì)列，消費(fèi)者在這個(gè)隊(duì)列里面消耗數(shù)據(jù)，生產(chǎn)者在這個(gè)里面生產(chǎn)數(shù)據(jù)
public PriorityQueue<Integer> queue = new PriorityQueue<Integer>(COUNT);
public static void main(String[] args) {
WaitAndNofityTest waitAndNofityTest = new WaitAndNofityTest();
Cus cus = waitAndNofityTest.new Cus();
Make make = waitAndNofityTest.new Make();
make.start();
cus.start();
}
//消費(fèi)者線程類(lèi)
class Cus extends Thread {
@Override
public void run() {
System.out.println("Cus queue size is:" + queue.size());
eatData();
}
public void eatData() {
while (true) {
synchronized (queue) {
System.out.println("go to eatData method size is:" + queue.size());
while (queue.size() == 0) {
try {
System.out.println("Cus start notify");
queue.notify();
System.out.println("Cus start wait");
queue.wait();
System.out.println("Cus wait after");
} catch (InterruptedException e) {
queue.notify();
}
}
queue.poll();
System.out.println("Cus eatData after size is:" + queue.size());
}
}
}
}
//生產(chǎn)者線程類(lèi)
class Make extends Thread {
@Override
public void run() {
System.out.println("Make queue size is:" + queue.size());
addData();
}
public void addData() {
while (true) {
synchronized (queue) {
System.out.println("go to addData method size is:" + queue.size());
while (queue.size() == COUNT) {
try {
System.out.println("Make start notify");
queue.notify();
System.out.println("Make start wait");
queue.wait();
System.out.println("Make wait after");
} catch (InterruptedException e) {
queue.notify();
}
}
queue.offer(5);
System.out.println("Cus addData after size is:" + queue.size());
}
}
}
}
}
四、部分運(yùn)行結(jié)果
Cus addData after size is:5
go to addData method size is:5
Make start notify
Make start wait
Cus wait after
Cus eatData after size is:4
go to eatData method size is:4
Cus eatData after size is:3
go to eatData method size is:3
Cus eatData after size is:2
go to eatData method size is:2
Cus eatData after size is:1
go to eatData method size is:1
Cus eatData after size is:0
go to eatData method size is:0
Cus start notify
Cus start wait
Make wait after
Cus addData after size is:1
go to addData method size is:1
Cus addData after size is:2
go to addData method size is:2
Cus addData after size is:3
go to addData method size is:3
Cus addData after size is:4
go to addData method size is:4
Cus addData after size is:5
go to addData method size is:5
Make start notify
Make start wait
Cus wait after
Cus eatData after size is:4
go to eatData method size is:4
Cus eatData after size is:3
go to eatData method size is:3
Cus eatData after size is:2
go to eatData method size is:2
Cus eatData after size is:1
go to eatData method size is:1
Cus eatData after size is:0
go to eatData method size is:0
Cus start notify
Cus start wait
Make wait after
Cus addData after size is:1
go to addData method size is:1
Cus addData after size is:2
go to addData method size is:2
Cus addData after size is:3
go to addData method size is:3
Cus addData after size is:4
go to addData method size is:4
Cus addData after size is:5
go to addData method size is:5
Make start notify
Make start wait
Cus wait after
Cus eatData after size is:4
go to eatData method size is:4
Cus eatData after size is:3
go to eatData method size is:3
Cus eatData after size is:2
go to eatData method size is:2
Cus eatData after size is:1
go to eatData method siz
如果運(yùn)行了不理解，你可以自己測(cè)試然后分析打印的數(shù)據(jù)，當(dāng)然你也可以注釋掉2個(gè)類(lèi)里面的任意一個(gè)notify方法，然后看是什么效果，是不是和自己分析的結(jié)果一樣，同樣你也可以去掉第一類(lèi)的wait方法試下，看執(zhí)行notify方法后是synchronized執(zhí)行完了呼喚其其它線程或則在調(diào)用wait方法之后釋放鎖后是否也會(huì)呼喚其線程？
五、用ArrayBlockingQueue實(shí)現(xiàn)阻塞式的生產(chǎn)者和消費(fèi)者
官方API
package wait;
import java.util.concurrent.ArrayBlockingQueue;
public class BlockTest {
private int COUNT = 5;
private ArrayBlockingQueue<Integer> queue = new ArrayBlockingQueue<Integer>(COUNT);
public static void main(String[] args) {
BlockTest test = new BlockTest();
Make make = test.new Make();
Cus cus = test.new Cus();
make.start();
cus.start();
}
class Cus extends Thread {
@Override
public void run() {
eatData();
}
private void eatData() {
while (true) {
try {
queue.take();
System.out.println("隊(duì)列取一個(gè)元素，隊(duì)列剩余"+queue.size() + "元素");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class Make extends Thread {
@Override
public void run() {
addData();
}
private void addData() {
while(true){
try {
queue.put(5);
System.out.println("隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：" + (COUNT-queue.size()));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
六、部分運(yùn)行結(jié)果
隊(duì)列取一個(gè)元素，隊(duì)列剩余4元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余3元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余2元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余1元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余0元素
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：4
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：3
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：2
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：1
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：0
隊(duì)列取一個(gè)元素，隊(duì)列剩余4元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余3元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余2元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余1元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余0元素
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：4
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：3
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：2
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：1
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：0
隊(duì)列取一個(gè)元素，隊(duì)列剩余4元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余3元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余2元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余1元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余0元素
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：4
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：3
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：2
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：1
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：0
隊(duì)列取一個(gè)元素，隊(duì)列剩余4元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余3元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余2元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余1元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余0元素
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：4
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：3
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：2
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：1
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：0
隊(duì)列取一個(gè)元素，隊(duì)列剩余4元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余3元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余2元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余1元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余0元素
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：4
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：3
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：2
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：1
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：0
隊(duì)列取一個(gè)元素，隊(duì)列剩余4元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余3元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余2元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余1元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余0元素
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：4
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：3
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：2
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：1
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：0
隊(duì)列取一個(gè)元素，隊(duì)列剩余4元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余3元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余2元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余1元素
隊(duì)列取一個(gè)元素，隊(duì)列剩余0元素
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：4
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：3
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：2
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：1
隊(duì)列插入一個(gè)元素，隊(duì)列剩余空間：0
隊(duì)列取一個(gè)元素，隊(duì)列剩余4元素
作者：chen.yu
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