Java n threads take turns printing numbers problem

One. Implement two threads. Take turns to print out numbers. For example, the following:

Bthread---10aThread---9bThread---8aThread---- -3bThread-2aThread-1

Implemented with the lock class in Java:

Package Com.yjq.thread_demo;import Java.util.concurrent.locks.lock;import Java.util.concurrent.locks.reentrantlock;public class Twothreadprinter {private Lock Threadlock = new Reentrantlock (); Private Boolean flag = false;int count = 10; Thread athread = new Thread (new Runnable () {public void run () {while (true) {//Lock threadlock.lock (); try {if (Count < 1 ) {return;} if (flag) {//Athread task System.out.println ("Athread--" + (count--)); flag =!flag;}} catch (Exception e) {//Todo:handle Exception} finally {//release lock Threadlock.unlock ();}}}); Thread bthread = new Thread (new Runnable () {public void run () {while (true) {//Lock threadlock.lock (); try {if (Count < 1 ) {return;} if (!flag) {//Athread task System.out.println ("Bthread-to" + (count--)); flag =!flag;}} catch (Exception e) {//Todo:handle Exception} finally {//release lock Threadlock.unlock ();}}}); public void Starttwothread () {Athread.start (); Bthread.start ();} public static void Main (string[] args) {Twothreadprinter Twothreadprinter = nEW Twothreadprinter (); Twothreadprinter.starttwothread ();}} 

Implemented with synchronized:

Package Com.yjq.thread_demo;public class TwoThreadPrinter2 {Private Object threadlock = new object (); int count = 10; Thread athread = new Thread (new Runnable () {public void run () {while (true) {//Lock synchronized (Threadlock) {if (Count &l T 1) {return;} Athread task System.out.println ("Athread--" + (count--)); Threadlock.notify (); try {threadlock.wait ();} catch (Exception e) {//Todo:handle Exception}}}); Thread bthread = new Thread (new Runnable () {public void run () {while (true) {//Lock synchronized (Threadlock) {if (Count &l T 1) {return;} Athread task System.out.println ("Bthread--" + (count--)); Threadlock.notify (); try {threadlock.wait ();} catch (Exception e) {//Todo:handle Exception}}}});p ublic void Starttwothread () {Athread.start (); Bthread.start ();} public static void Main (string[] args) {Twothreadprinter twothreadprinter = new Twothreadprinter (); Twothreadprinter.starttwothread ();}}

Using the Lock class method is easier to understand. The block between lock () and Unlock () is locked

The Synchronize method uses less flag to flag which thread to print, because the thread lock's notifity () method releases the lock and wakes other threads, and the Wait () method of the thread lock releases the lock and sleeps the current thread, assuming that there are just two threads, Then it is natural to start with a thread and hibernate this thread.

Two. Scaling to n threads the problem of printing numbers in turn

n Threads print numbers in turn. Using the lock class is easier to extend

For example, three threads take turns to print a number

Package Com.myexample.test;import Java.util.concurrent.locks.lock;import Java.util.concurrent.locks.ReentrantLock ;p Ublic class Threethreadprinter {private Lock Threadlock = new Reentrantlock ();p rivate int flag = 0;int count = 10; Thread athread = new Thread (new Runnable () {public void run () {while (true) {//Lock threadlock.lock (); try {if (Count < 1 ) {return;} if (count%3 = = 0) {//Athread task System.out.println ("Athread--" + count); count--;}} catch (Exception e) {//Todo:handle Exception} finally {//release lock Threadlock.unlock ();}}}); Thread bthread = new Thread (new Runnable () {public void run () {while (true) {//Lock threadlock.lock (); try {if (Count < 1 ) {return;} if (count%3 = = 1) {//Athread task System.out.println ("Bthread--" + count); count--;}} catch (Exception e) {//Todo:handle Exception} finally {//release lock Threadlock.unlock ();}}}); Thread cthread = new Thread (new Runnable () {public void run () {while (true) {//Lock threadlock.lock (); try {if (Count < 1 ) {return;} if (count%3 = =2) {//Athread task System.out.println ("Cthread--" + count); count--;}} catch (Exception e) {//Todo:handle Exception} finally {//release lock Threadlock.unlock ();}}}); public void Starttwothread () {Athread.start (); Bthread.start (); Cthread.start ();} public static void Main (string[] args) {Threethreadprinter twothreadprinter = new Threethreadprinter (); Twothreadprinter.starttwothread ();}}

Output results

Bthread---10aThread---9cThread---8bThread---- -3cThread-2bThread-1

Java n threads take turns printing numbers problem