java多线程 关于synchronized wait notify CountDownLatch CyclicBarrier Semaphore

package com.my.JavaThread;

import java.util.Random;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;
import java.util.concurrent.Semaphore;

public class CountDownTest {
private static void runDAfterABC() {
int worker = 3;
final CountDownLatch countDownLatch = new CountDownLatch(worker);
new Thread(new Runnable() {
@Override
public void run() {
System.out.println("D is waiting for other three threads");
try {
countDownLatch.await();
System.out.println("All done, D starts working");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
for (char threadName = 'A'; threadName <= 'C'; threadName++) {
final String tN = String.valueOf(threadName);
new Thread(new Runnable() {
@Override
public void run() {
System.out.println(tN + "is working");
try {
Thread.sleep(100);
} catch (Exception e) {
e.printStackTrace();
}
System.out.println(tN + "finished");
countDownLatch.countDown();
}
}).start();
}
}

private static void demo3() {
final Object lock = new Object();
Thread B = new Thread(new Runnable() {
@Override
public void run() {
synchronized (lock) {
System.out.println("B 1");
System.out.println("B 2");
System.out.println("B 3");
lock.notify();
}
}
});
Thread A = new Thread(new Runnable() {
@Override
public void run() {
synchronized (lock) {
System.out.println("A 1");
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("A 2");
System.out.println("A 3");
}
}
});
A.start();
B.start();

}

private static void runABCWhenAllReady() {
int runner = 3;
final CyclicBarrier cyclicBarrier = new CyclicBarrier(runner);
final Random random = new Random();
for (char runnerName = 'A'; runnerName <= 'C'; runnerName++) {
final String rN = String.valueOf(runnerName);
new Thread(new Runnable() {
@Override
public void run() {
long prepareTime = random.nextInt(10000) + 100;
System.out.println(rN + "is preparing for time:" + prepareTime);
try {
Thread.sleep(prepareTime);
} catch (Exception e) {
e.printStackTrace();
}
try {
System.out.println(rN + "is prepared, waiting for others");
cyclicBarrier.await(); // 当前运动员准备完毕，等待别人准备好
} catch (InterruptedException e) {
e.printStackTrace();
} catch (BrokenBarrierException e) {
e.printStackTrace();
}
System.out.println(rN + "starts running"); // 所有运动员都准备好了，一起开始跑
}
}).start();
}
}

private static void doTaskWithResultInWorker() {
Callable<Integer> callable = new Callable<Integer>() {
@Override
public Integer call() throws Exception {
System.out.println("Task starts");
Thread.sleep(1000);
int result = 0;
for (int i=0; i<=101; i++) {
result += i;
}
System.out.println("Task finished and return result");
return result;
}
};
FutureTask<Integer> futureTask = new FutureTask<>(callable);
new Thread(futureTask).start();
try {
System.out.println("Before futureTask.get()");
System.out.println("Result:" + futureTask.get());
System.out.println("After futureTask.get()");
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}

public static void semaphoretest() {
//采用新特性来启动和管理线程——内部使用线程池
ExecutorService exec = Executors.newCachedThreadPool();
//只允许2个线程同时访问
final Semaphore semp = new Semaphore(1);
//模拟5个客户端访问
Object lock = new Object();

for (int index = 0; index < 5; index++){
synchronized (lock) {
final int num = index;
Runnable run = new Runnable() {
public void run() {
try {
//获取许可
semp.acquire();
System.out.println("线程" +
Thread.currentThread().getName() + "获得许可："  + num);
//模拟耗时的任务
for (int i = 0; i < 999999; i++) ;
//释放许可
semp.release();
System.out.println("线程" +
Thread.currentThread().getName() + "释放许可："  + num);
System.out.println("当前允许进入的任务个数：" +
semp.availablePermits());
}catch(InterruptedException e){
e.printStackTrace();
}
}
};
exec.execute(run);
lock.notify();
}
}
//关闭线程池
exec.shutdown();
}

public static void main(String[] args) {
//		CountDownTest.runDAfterABC();
//		System.out.println("-------");
CountDownTest.demo3();
//		CountDownTest.runABCWhenAllReady();
//		CountDownTest.doTaskWithResultInWorker();
//		CountDownTest.semaphoretest();
}
}