Explaining Java base class methods through the producer consumer model Wait, notify, Notifyall

Wait (), notify (), and Notifyall () are all methods of the Java base class Java.lang.Object.

Popular explanations
Wait (): Waits for another thread to wake up on the current thread.
Notify (): Wakes up a thread that is waiting for this object's monitor.
Notifyall (): Wakes up all the threads waiting on this object monitor.
These three methods are the underlying mechanism provided by the Java language to implement inter-thread blocking (Blocking) and control in-process scheduling (inter-process communication).
The use of these three methods is explained below through a producer/consumer example.

/** * consumer * Created by Wiki on 16/1/28. */public class Customer implements Runnable {private String    Name    Private channel channel;        Public Customer (String name, channel Channel) {this.name = name;    This.channel = Channel;            @Override public void Run () {while (true) {Good good = Channel.get ();            if (good! = null) {SYSTEM.OUT.PRINTLN (name + "Get product:" + good.getname ());  } else {synchronized (channel) {try {System.out.println (name +                        "Enter Wait");                    Channel.wait ();                    } catch (Interruptedexception e) {e.printstacktrace (); }                }            }        }    }}

/** * producer * Created by Wiki on 16/1/28. */public class Producer implements Runnable {private static    volatile int goodnumber = 0;    private String name;    Private channel channel;        Public Producer (String name, channel Channel) {this.name = name;    This.channel = Channel;            @Override public void Run () {while (true) {int sleep = new Random (). Nextint (2000);            try {thread.sleep (sleep);            } catch (Interruptedexception e) {e.printstacktrace ();            } Good good = new Good ("Item-Number" + (++goodnumber));            SYSTEM.OUT.PRINTLN (name + "Production goods:" + good.getname ());        Channel.put (good); }    }}

/** * Goods * Created by Wiki on 16/1/28. */public class Good {    private String name;    Public good (String name) {        this.name = name;    }    Public String GetName () {        return name;    }    public void SetName (String name) {        this.name = name;    }}

/** * Consumption channel * Created by Wiki on 16/1/28. */public class Channel {    private queue<good> goodlist = new linkedlist<> ();    Public synchronized Good Get () {        if (goodlist.size () = = 0) {            return null;        }        Good good = Goodlist.remove ();        return good;    }    Public synchronized void put (good good) {        goodlist.add (good);//        Notifyall ();        Notify ();    }}

public class Main {public    static void Main (string[] args) {        channel channel = new Channel ();        New Thread (New Producer ("Producer 1", channel)). Start ();        New Thread (New Producer ("Producer 2", channel)). Start ();        New Thread (New Producer ("Producer 2", channel)). Start ();        New Thread (New Customer ("Consumer 1", channel)). Start ();        New Thread (New Customer ("Consumer 2", channel)). Start ();        New Thread (New Customer ("Consumer 3", channel)). Start ();    }}

Run result analysis One (notify):

Each time a product is called notify, only one consumer is awakened to consume, and the awakening principle is the longest waiting time to start.

Consumer 1 into wait
Consumer 2 into wait
Consumer 3 into wait
Producer 1 Production commodities: Goods-No. 1
Consumer 1 Get Product: Item-No. 1
Consumer 1 into wait
Producer 2 Production commodities: Goods-No. 2
Consumer 2 Get Product: Item-No. 2
Consumer 2 into wait
Producer 2 Production commodities: Goods-No. 3
Consumer 3 Get Product: Item-No. 3
Consumer 3 into wait
Producer 1 Production commodities: Goods-No. 4
Consumer 1 Get Product: Item-No. 4
Consumer 1 into wait
Producer 1 Production commodities: Goods-No. 5
Consumer 2 Get Product: Item-No. 5
Consumer 2 into wait
...

Run Results Analysis II (change notify to Notifyall):

Every product that is produced is called Notifyall, and all consumers are awakened.

Consumer 1 into wait
Consumer 3 into wait
Consumer 2 into wait
Producer 2 Production commodities: Goods-No. 1
Consumer 3 into wait
Consumer 2 Get Product: Item-No. 1
Consumer 1 into wait
Consumer 2 into wait
Producer 2 Production commodities: Goods-No. 2
Consumer 2 Get Product: Item-No. 2
Consumer 1 into wait
Consumer 3 into wait
Consumer 2 into wait
Producer 2 Production commodities: Goods-No. 3
Consumer 2 Get Product: Item-No. 3
...

Source: http://www.taoweiji.cn/index.php/archives/112

Explaining Java base class methods through the producer consumer model Wait, notify, Notifyall