Thread threads consumer and producer problem Code __java multithreading

Recently reviewed the thread, found running consumer and producer code parts, there will always be first consumption after production.

The source code is as follows:

public class Producerconsumer {public static void main (string[] args) {syncstack ss = new Syncsta
               CK ();
               Producer p = new Producer (ss);
               Consumer C = new Consumer (ss);
               New Thread (P). Start ();
               New Thread (P). Start ();

               New Thread (P). Start ();
               New Thread (c). Start ();
               New Thread (c). Start ();
        New Thread (c). Start ();
        } class Wotou {int id;
        Wotou (int id) {this.id = ID;
        Public String toString () {return "Wotou:" + ID;
        } class Syncstack {int index = 0;
       
        wotou[] ARRWT = new Wotou[6];
               Public synchronized void push (Wotou wt) {//is not available here, if interruptedexception occurs, it jumps out of the IF statement and continues down
                              The while will return the execution while (index = = arrwt.length) {try { This.wait()//The thread that locked the current object stops (if the current object is already locked)} catch (Interruptedexception e) {E
                       . Printstacktrace ();             
               } this.notifyall ();
               Arrwt[index] = WT;
        Index + +; The public synchronized Wotou pop () {//is not allowed to use if, if interruptedexception occurs, it jumps out of the IF statement and continues down// While it returns the execution while (index = = 0) {try {this.wait ();//Lock The thread holding the current object stops (if the current object is already locked)} catch (Interruptedexception e) {E.print
                       StackTrace ();
               } this.notifyall ();
               index--;
        return Arrwt[index];
        } class Producer implements Runnable {Syncstack SS = null;
        Producer (Syncstack ss) {THIS.SS = SS;
public void Run () {               for (int i=0; i<20; i++) {Wotou wt = new Wotou (i);
Ss.push (WT);
                       System.out.println ("produced:" + wt);
                       try {thread.sleep ((int) (Math.random () * 200));
                       catch (Interruptedexception e) {e.printstacktrace ();
        Class Consumer implements Runnable {Syncstack SS = null;
        Consumer (Syncstack ss) {THIS.SS = SS; public void Run () {for (int i=0; i<20; i++) {Wotou wt = Ss.pop
();
                       System.out.println ("Consumption:" + wt);
                       try {thread.sleep ((int) (Math.random () * 1000));
                       catch (Interruptedexception e) {e.printstacktrace ();                 }    
               }
        }
}
 

Run Result:
Consumption: wotou:0
Produced: wotou:0
Produced: Wotou:1
Produced: Wotou:2
Produced: Wotou:3
Produced: Wotou:4
Consumption: Wotou:4
Produced: Wotou:5
Produced: Wotou:6
Produced: Wotou:7
Consumption: Wotou:7
Produced: Wotou:8
Consumption: Wotou:8
Produced: Wotou:9
Consumption: Wotou:9
Produced: Wotou:10
Consumption: wotou:10
Produced: Wotou:11
Consumption: wotou:11
Produced: Wotou:12
Produced: Wotou:13
Consumption: Wotou:12
Produced: Wotou:14
Consumption: wotou:13
Consumption: wotou:14
Produced: wotou:15
Consumption: wotou:15
Produced: Wotou:16
Consumption: wotou:16
Produced: Wotou:17
Consumption: wotou:17
Produced: Wotou:18
Consumption: wotou:18
Produced: wotou:19
Consumption: wotou:19
Consumption: Wotou:6
Consumption: Wotou:5
Consumption: Wotou:3
Consumption: Wotou:2
Consumption: wotou:1

There should be a problem with the thread, and when the push () method is finished, to print the first few, another thread executes, leading to consumption before production.

Modify code: Put the print part in the push () and Pop () methods while the Pop () method returns the type void.

The code is as follows:

public class Producerconsumer {public static void main (string[] args) {syncstack ss = new Syncsta
               CK ();
               Producer p = new Producer (ss);
               Consumer C = new Consumer (ss);
 
               New Thread (P). Start ();
        New Thread (c). Start ();
        } class Wotou {int id;
        Wotou (int id) {this.id = ID;
        Public String toString () {return "Wotou:" + ID;
        } class Syncstack {int index = 0;
       
        wotou[] ARRWT = new Wotou[6];
                               Public synchronized void push (Wotou wt) {while (index = = arrwt.length) {try {
                       This.wait ();
                       catch (Interruptedexception e) {e.printstacktrace ();             
               } this.notifyall ();
                Arrwt[index] = WT; Index + +;
        System.out.println ("produced:" + wt);
                               public synchronized void Pop () {while (index = = 0) {try {
                       This.wait ();
                       catch (Interruptedexception e) {e.printstacktrace ();
               } this.notifyall ();
               index--;
        System.out.println ("Consumption:" + Arrwt[index]);
        } class Producer implements Runnable {Syncstack SS = null;
        Producer (Syncstack ss) {THIS.SS = SS; public void Run () {for (int i=0; i<20; i++) {Wotou wt = new Wo
                       Tou (i);
                      
                       Ss.push (WT);
                       try {thread.sleep ((int) (Math.random () * 200));
           catch (Interruptedexception e) {                    E.printstacktrace ();
        Class Consumer implements Runnable {Syncstack SS = null;
        Consumer (Syncstack ss) {THIS.SS = SS;
                      
                       public void Run () {for (int i=0; i<20; i++) {ss.pop ();
                       try {thread.sleep ((int) (Math.random () * 1000));
                       catch (Interruptedexception e) {e.printstacktrace ();
 }                     
               }
        }
}