交替输出

交替输出

题目：线程 1 输出 a 5 次，线程 2 输出 b 5 次，线程 3 输出 c 5 次。现在要求输出 abcabcabcabcabc

wait notify 版

public class SyncWaitNotify {private volatile int flag;private volatile int loopNumber;public SyncWaitNotify(int flag,int loopNumber){this.flag = flag;this.loopNumber = loopNumber;}public void print(int flag,int next,String str){for(int i=0;i<loopNumber;i++){synchronized (this){while (this.flag != flag){try {this.wait();} catch (InterruptedException e) {e.printStackTrace();}}System.out.print(str);this.flag = next;this.notifyAll();}}}public static void main(String[] args) {SyncWaitNotify syncWaitNotify = new SyncWaitNotify(1,5);new Thread(() -> {syncWaitNotify.print(1,2,"a");}).start();new Thread(() -> {syncWaitNotify.print(2,3,"b");}).start();new Thread(() -> {syncWaitNotify.print(3,1,"c");}).start();}
}

Lock 条件变量版

public class AwaitSignal extends ReentrantLock {private volatile int loopNumber;public AwaitSignal(int loopNumber) {this.loopNumber = loopNumber;}public void print(Condition condition,Condition next,String str){for(int i=0;i<loopNumber;i++){this.lock();try {try {condition.await();System.out.print(str);next.signal();} catch (InterruptedException e) {e.printStackTrace();}} finally {this.unlock();}}}public void start(Condition condition){this.lock();try {condition.signal();} finally {this.unlock();}}public static void main(String[] args) {AwaitSignal awaitSignal = new AwaitSignal(5);Condition aWait = awaitSignal.newCondition();Condition bWait = awaitSignal.newCondition();Condition cWait = awaitSignal.newCondition();new Thread(() -> {awaitSignal.print(aWait,bWait,"a");}).start();new Thread(() -> {awaitSignal.print(bWait,cWait,"b");}).start();new Thread(() -> {awaitSignal.print(cWait,aWait,"c");}).start();awaitSignal.start(aWait);}
}

Park Unpark 版

public class SyncPark {private int loopNumber;public Thread[] threads;public SyncPark(int loopNumber){this.loopNumber = loopNumber;}public void print(int next,String str){for(int i=0;i<loopNumber;i++){LockSupport.park();System.out.print(str);LockSupport.unpark(threads[next]);}}public void start(Thread thread){LockSupport.unpark(thread);}public static void main(String[] args) {SyncPark syncPark = new SyncPark(5);Thread t1 = new Thread(() -> {syncPark.print(1, "a");}, "t1");Thread t2 = new Thread(() -> {syncPark.print(2, "b");}, "t2");Thread t3 = new Thread(() -> {syncPark.print(0, "c");}, "t3");syncPark.threads = new Thread[]{t1,t2,t3};t1.start();t2.start();t3.start();syncPark.start(t1);}
}