Java Threads and concurrent programming practices----waiting for notifications (producer consumer issues) threads

Java provides a set of APIs to support the interaction between threads. A set of APIs waiting to be notified in the object class

Wait ()

Notify ()

Notifyall ()

It is important to note that you must never call the Wait () method outside of the loop. (Open a separate article to discuss)

The following uses consumer and producer issues to demonstrate the use of the above API:

Package xiancheng;public class pc {public static void main (String[]  args)  {shared s = new shared (); Thread t1 = new thread (New product (s)); Thread t2 = new thread (New consumer (s)); T1.start (); T2.start ();}} class shared {private char c;private volatile boolean writeable =  true;public synchronized void setchar (char ch)  {while (!writeable)  {try  {wait ();}  catch  (interruptedexception e)  {e.printstacktrace ();}} This.c = ch;writeable = false;notify ();} Public synchronized char getchar ()  {while (writeable)  {try {wait ();}  catch  (interruptedexception e)  {e.printstacktrace ();}} Writeable = true;notify (); return c;}} Class product implements runnable{private shared s;public product (Shared s)  {this.s = s;} @Overridepublic  void run ()  {for  (char i =  ' A '; i <  ' Z ';  i++)  {s.setchar (i); System.out.println ("producer produces a"  + i);}}} Class consumer implements runnable{private shared s;public consumer (Shared  s)  {this.s = s;} @Overridepublic  void run ()  {char ch;do {ch = s.getchar (); SYSTEM.OUT.PRINTLN ("Consumer consumes a"  + ch);}  while  (ch !=  ' Z ');}}

Printing results:

Consumers consume a producer of a a producers produced a producer of a B consumer consumption a B producer produced a C consumer consumption a C producer produced a D consumer consumption a D producer produced an e consumer consumption an e producer produced a f consumer consumption an F producer produced a G consumer Cost A G producer produced an H consumer spending an H producer produced a I consumer consumption a I producer produced a J consumer consumption a J producer produced a K consumer consumption a K producer produced a l producer produced a m consumer consumption a m producer produces an L consumer consumes a n consumers consume an n producer produced an O consumer consumption an O producer produced a P consumer consumption a p producer produced a Q consumer consumption a Q producer produced an R consumer spending a r producer produced a s consumer spending a s producer produced a T consumer consuming a T producer produced a u consumer consumes a U producer produced a V consumer consumption a V producer produced a W consumer consumed a W producer produced an X consumer consumption an X producer produced a Y consumer spending a a Y

Obviously the 12th line has a problem, the consumption appears before the production, look at the code to know that the production and consumption sequence is not chaotic, but the printing order is not correct, because the wake-up action is before printing,

The improvement code is as follows:

Package xiancheng;public class pc {public static void main (String[]  args)  {shared s = new shared (); Thread t1 = new thread (New product (s)); Thread t2 = new thread (New consumer (s)); T1.start (); T2.start ();}} class shared {private char c;private volatile boolean writeable =  true;public synchronized void setchar (char ch)  {while (!writeable)  {try  {wait ();}  catch  (interruptedexception e)  {e.printstacktrace ();}} This.c = ch;writeable = false;notify ();} Public synchronized char getchar ()  {while (writeable)  {try {wait ();}  catch  (interruptedexception e)  {e.printstacktrace ();}} Writeable = true;notify (); return c;}} class product implements runnable{private final shared s;public  Product (Shared s)  {this.s = s;} @Overridepublic  void run ()  {for  (char i =  ' A '; i <  ' Z ';  i++)  {synchronized (s)  {s.setchar (i); System.out.println ("producer produces a"  + i);}}}} Class consumer implements runnable{private final shared s;public consumer ( shared s)  {this.s = s;} @Overridepublic  void run ()  {char ch;do {synchronized (s)  {ch =  S.getchar (); SYSTEM.OUT.PRINTLN ("Consumer consumes a"  + ch);}}  while  (ch !=  ' Z ');}}

Operation Result:

Producers produced a consumer consumption of a a producer produced a B consumer consumption a B producer produced a C consumer consumption a C producer produced a D consumer consumption a D producer produced an e consumer consumption an e producer produced a f consumer consumption an F producer produced a G consumer Cost A G producer produced an H consumer spending an H producer produced a I consumer consuming a I producer produced a J consumer consumption a J producer produced a K consumer consumption a K producer produced a l consumer consumption a l producer produced a m consumer consumption a m producer produces a n consumers consume an n producer produced an O consumer consumption an O producer produced a P consumer consumption a p producer produced a Q consumer consumption a Q producer produced an R consumer spending a r producer produced a s consumer spending a s producer produced a T consumer consuming a T producer produced a u consumer consumes a U producer produced a V consumer consumption a V producer produced a W consumer consumed a W producer produced an X consumer consumption an X producer produced a Y consumer spending a a Y

Java Threads and concurrent programming practices----waiting for notifications (producer consumer issues) threads