题目描述

建立三个线程A、B、C，A线程打印10次字母A，B线程打印10次字母B,C线程打印10次字母C，但是要求三个线程同时运行，并且实现交替打印，即按照ABCABCABC的顺序打印。

5种方法

使用synchronized, wait和notifyAll使用Lock->ReentrantLock 和 state标志使用Lock->ReentrantLock 和Condition（await 、signal、signalAll）使用Semaphore使用AtomicInteger扩展：采用join实现(一次性打印)

5.1 使用synchronized, wait和notifyAll

public class ABC7 {private static Object o = new Object();//所对象private static int state = 0;//控制顺序private static int PRINT_NUMBER = 10;//打印次数private static int THREAD_NUM = 3;//线程数量static class ThreadGenetic implements Runnable {char name;int data;public ThreadGenetic(char name, int data){this.name = name;this.data = data;}public void run() {synchronized (o) {for(int i = 0; i < PRINT_NUMBER; ) {if(state % THREAD_NUM == data){//保证顺序 System.out.print(name);++ state;i++;//注意保证迭代次数 o.notifyAll();}else{try {o.wait();} catch (InterruptedException e) {e.printStackTrace();}}}}}}public static void main(String[] args) {new Thread(new ThreadGenetic('B',1)).start();new Thread(new ThreadGenetic('A',0)).start();new Thread(new ThreadGenetic('C',2)).start();}}

5.2 使用Lock->ReentrantLock 和 state标志

import java.util.concurrent.locks.ReentrantLock;public class ABC {private static int state = 0;//控制顺序private static int PRINT_NUMBER = 10;//打印次数private static int THREAD_NUM = 3;//线程数量private static ReentrantLock lock = new ReentrantLock();//锁static class ThreadGenetic extends Thread{char name;int data;public ThreadGenetic(char name, int data){this.name = name;this.data = data;}public void run(){for (int i = 0; i < PRINT_NUMBER; ) {//确保打印次数lock.lock();if(state % THREAD_NUM == this.data){//确保按顺序打印System.out.print(this.name);state++; //确保按顺序打印i++; //确保打印次数}lock.unlock();}}}public static void main(String[] args) {new ThreadGenetic('B',1).start();new ThreadGenetic('C',2).start();new ThreadGenetic('A',0).start();}}

5.3 使用Lock->ReentrantLock 和Condition（await 、signal、signalAll）

方法1

import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.ReentrantLock;public class ABC8 {private static int state = 0;//控制顺序private static int PRINT_NUMBER = 10;//打印次数private static int THREAD_NUM = 3;//线程数量private static ReentrantLock lock = new ReentrantLock();//锁private static Condition condition = lock.newCondition();static class ThreadGenetic extends Thread{char name;int data;public ThreadGenetic(char name, int data){this.name = name;this.data = data;}public void run(){lock.lock();try {for (int i = 0; i < PRINT_NUMBER; ) {//确保打印次数while(state % THREAD_NUM != data){//确保按顺序打印 condition.await();}System.out.print(name);state++; //确保按顺序打印i++; //确保打印次数condition.signalAll();}} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}lock.unlock();}}public static void main(String[] args) {new ThreadGenetic('B',1).start();new ThreadGenetic('C',2).start();new ThreadGenetic('A',0).start();}}

方法2

import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.ReentrantLock;public class ABC2 {private static int state = 0;//控制顺序private static int PRINT_NUMBER = 10;//打印次数private static int THREAD_NUM = 3;//线程数量private static ReentrantLock lock = new ReentrantLock();//锁private static Condition conditionA = lock.newCondition();private static Condition conditionB = lock.newCondition();private static Condition conditionC = lock.newCondition();static class ThreadGenetic extends Thread{char name;int data;Condition condition1;Condition condition2;public ThreadGenetic(char name, int data, Condition condition1,Condition condition2){this.name = name;this.data = data;this.condition1 = condition1;this.condition2 = condition2;}public void run(){lock.lock();try {for (int i = 0; i < PRINT_NUMBER; ) {//确保打印次数while(state % THREAD_NUM != data){//确保按顺序打印 condition1.await();}System.out.print(name);state++; //确保按顺序打印i++; //确保打印次数condition2.signal();}} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}lock.unlock();}}public static void main(String[] args) {new ThreadGenetic('B',1,conditionB,conditionC).start();new ThreadGenetic('C',2,conditionC,conditionA).start();new ThreadGenetic('A',0,conditionA,conditionB).start();}}

5.4 使用Semaphore

import java.util.concurrent.Semaphore;public class ABC3 {private static int PRINT_NUMBER = 10;//打印次数private static Semaphore semaphoreA = new Semaphore(1);private static Semaphore semaphoreB = new Semaphore(1);private static Semaphore semaphoreC = new Semaphore(1);static class ThreadGenetic extends Thread{char name;int data;Semaphore semaphore1;Semaphore semaphore2;public ThreadGenetic(char name, Semaphore semaphore1,Semaphore semaphore2){this.name = name;this.semaphore1 = semaphore1;this.semaphore2 = semaphore2;}public void run(){for (int i = 0; i < PRINT_NUMBER; i++) {//确保打印次数try {semaphore1.acquire();System.out.print(name);semaphore2.release();} catch (InterruptedException e) {e.printStackTrace();}}}}public static void main(String[] args) {try {semaphoreB.acquire();//保证A先于BC开始 semaphoreC.acquire();} catch (InterruptedException e) {e.printStackTrace();}new ThreadGenetic('B',semaphoreB,semaphoreC).start();new ThreadGenetic('C',semaphoreC,semaphoreA).start();new ThreadGenetic('A',semaphoreA,semaphoreB).start();}}

5.5 使用AtomicInteger

import java.util.concurrent.atomic.AtomicInteger;public class ABC5 { private static AtomicInteger atomicinteger = new AtomicInteger(0);private static final int MAX_SYC_VALUE = 3 * 10;static class ThreadGenetic extends Thread {char name;int data;public ThreadGenetic(char name, int data) {this.name = name;this.data = data;}public void run() {while (atomicinteger.get() < MAX_SYC_VALUE-1) {if (atomicinteger.get() % 3 == data) {System.out.print(name);atomicinteger.getAndIncrement();}}}}public static void main(String[] args) {new ThreadGenetic('B', 1).start();new ThreadGenetic('C', 2).start();new ThreadGenetic('A', 0).start();}}

5.6采用join实现(一次性打印)

public class ABC6 {public static void main(String[] args) {// 线程Afinal Thread a = new Thread(new Runnable() {@Overridepublic void run() {System.out.println("A");}});// 线程Bfinal Thread b = new Thread(new Runnable() {@Overridepublic void run() {try {// 执行b线程之前，加入a线程,让a线程执行a.join();} catch (InterruptedException e) {e.printStackTrace();}System.out.println("B");}});// 线程Cfinal Thread c = new Thread(new Runnable() {@Overridepublic void run() {try {// 执行c线程之前，加入b线程,让b线程执行b.join();} catch (InterruptedException e) {e.printStackTrace();}System.out.println("C");}});// 启动三个线程 a.start();b.start();c.start();}}

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