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1、如何实现多线程交替打印字母和数字，打印效果：A1B2C3D4…

Automic

public class AutomicWay {volatile static char num1 = 'A';volatile static int num2 = 1;static AtomicInteger atomicInteger = new AtomicInteger(1);public static void main(String[] args) {new Thread(() -> {for (int i = 0; i < 26; i++) {while (atomicInteger.get() != 1) {}System.out.print(num1++);atomicInteger.set(2);}}).start();new Thread(() -> {for (int i = 0; i < 26; i++) {while (atomicInteger.get() != 2) {}System.out.print(num2++);atomicInteger.set(1);}}).start();}
}

BlockingQueue

public class BlockingQueueWay {volatile static char num1 = 'A';volatile static int num2 = 1;public static void main(String[] args) {BlockingQueue queue1 = new ArrayBlockingQueue(1);BlockingQueue queue2 = new ArrayBlockingQueue(1);new Thread(() -> {try {for (int i = 0; i < 26; i++) {System.out.print(num1++);queue2.put("到你");queue1.take();}} catch (InterruptedException e) {e.printStackTrace();}}).start();new Thread(() -> {try {for (int i = 0; i < 26; i++) {queue2.take();System.out.print(num2++);queue1.put("到你");}} catch (InterruptedException e) {e.printStackTrace();}}).start();}
}

ReentrantLock

public class ConditionWay {volatile static char num1 = 'A';volatile static int num2 = 1;public static void main(String[] args) {ReentrantLock lock = new ReentrantLock();Condition conditionA = lock.newCondition();Condition conditionB = lock.newCondition();new Thread(() -> {try {lock.lock();for (int i = 0; i < 26; i++) {System.out.print(num1++);conditionB.signal();conditionA.await();}conditionB.signal();} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}).start();new Thread(() -> {try {lock.lock();for (int i = 0; i < 26; i++) {System.out.print(num2++);conditionA.signal();conditionB.await();}conditionA.signal();} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}).start();}
}

LockSupport

public class LockSupportWay {static Thread t1,t2 =null;volatile static char num1 = 'A';volatile static int num2 = 1;public static void main(String[] args) {t1 = new Thread(()->{for (int i = 0; i < 26; i++) {System.out.print(num1++);LockSupport.unpark(t2);LockSupport.park(t1);}});t2 = new Thread(()->{for (int i = 0; i < 26; i++) {LockSupport.park(t2);System.out.print(num2++);LockSupport.unpark(t1);}});t1.start();t2.start();}
}

SynchronizedWaitNotify

public class SyncWaitNotifyWay {volatile static char num1 = 'A';volatile static int num2 = 1;public static volatile boolean flag = false;public static void main(String[] args) {Object o = new Object();new Thread(()->{synchronized (o){flag = true;for (int i = 0; i < 26; i++) {System.out.print(num1++);try {o.notify();o.wait();} catch (InterruptedException e) {e.printStackTrace();}}o.notify();}}).start();new Thread(()->{synchronized (o){// 只是为了保证执行A的先跑// while (!flag){// 	try {// 		o.wait();// 	} catch (InterruptedException e) {// 		e.printStackTrace();// 	}// }for (int i = 0; i < 26; i++) {System.out.print(num2++);try {o.notify();o.wait();} catch (InterruptedException e) {e.printStackTrace();}}o.notify();}}).start();}
}

TransferQueueWay

public class TransferQueueWay {volatile static char num1 = 'A';volatile static int num2 = 1;public static void main(String[] args) {TransferQueue transferQueue = new LinkedTransferQueue();new Thread(() -> {try {for (int i = 0; i < 26; i++) {System.out.print(transferQueue.take());transferQueue.transfer(num2++);}} catch (InterruptedException e) {e.printStackTrace();}}).start();new Thread(() -> {try {for (int i = 0; i < 26; i++) {transferQueue.transfer(num1++);System.out.print(transferQueue.take());}} catch (InterruptedException e) {e.printStackTrace();}}).start();}}

2、实现多个线程顺序打印abc

核心代码

public class PrintABC {ReentrantLock lock = new ReentrantLock();Condition conditionA = lock.newCondition();Condition conditionB = lock.newCondition();Condition conditionC = lock.newCondition();private int count;public PrintABC(int count) {this.count = count;}volatile int value = 0;public void printABC() {new Thread(new ThreadA()).start();new Thread(new ThreadB()).start();new Thread(new ThreadC()).start();}class ThreadA implements Runnable {@Overridepublic void run() {lock.lock();try {for (int i = 0; i < count; i++) {while (value % 3 != 0) {conditionA.await();}System.out.print("A");conditionB.signal();value++;}} catch (InterruptedException e) {e.printStackTrace();}}}class ThreadB implements Runnable {@Overridepublic void run() {lock.lock();try {for (int i = 0; i < count; i++) {while (value % 3 != 1) {conditionB.await();}System.out.print("B");conditionC.signal();value++;}} catch (InterruptedException e) {e.printStackTrace();}}}class ThreadC implements Runnable {@Overridepublic void run() {lock.lock();try {for (int i = 0; i < count; i++) {while (value % 3 != 2) {conditionC.await();}System.out.print("C");conditionA.signal();value++;}} catch (InterruptedException e) {e.printStackTrace();}}}
}

测试代码

public static void main(String[] args) {PrintABC printABC = new PrintABC(10);printABC.printABC();
}// 输出结果：ABCABCABCABCABCABCABCABCABCA

3、实现阻塞队列

核心代码

public class ProviderConsumer<T> {private int length;private Queue<T> queue;private ReentrantLock lock = new ReentrantLock();private Condition provideCondition = lock.newCondition();private Condition consumeCondition = lock.newCondition();public ProviderConsumer(int length) {this.length = length;this.queue = new LinkedList<>();}public void provide(T product) {lock.lock();try {while (queue.size() >= length) { // 不能换成if，唤醒后，可能条件已经不满足了provideCondition.await();}queue.add(product);consumeCondition.signal();} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}public T consume() {lock.lock();try {while (queue.isEmpty()) { // 不能换成if，唤醒后，可能条件已经不满足了consumeCondition.await();}T product = queue.remove();provideCondition.signal();return product;} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}return null;}
}

测试代码

public static void main(String[] args) {ProviderConsumer<Integer> providerConsumer = new ProviderConsumer<>(5);new Thread(() -> {for (int i = 0; i < 10; i++) {providerConsumer.provide(1);}}).start();new Thread(() -> {for (int i = 0; i < 10; i++) {providerConsumer.provide(2);}}).start();new Thread(() -> {for (int i = 0; i < 100; i++) {try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(providerConsumer.consume());}}).start();
}