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Week4Homework02.java
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246 lines (218 loc) · 6.47 KB
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package homework;
import java.util.Arrays;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
/**
* 作业： 思考有多少种方式，在 main 函数启动一个新线程，运行一个方法，拿到这 个方法的返回值后，退出主线程?
*
* @author liuby
*
*/
public class Week4Homework02 {
public static void main(String[] args) throws InterruptedException, ExecutionException, BrokenBarrierException {
long start = System.currentTimeMillis();
useFuture();
// useFutureTask();
// useCompletableFuture();
// useJoin();
// useLock();
// useLockSupport();
// useObjectWait();
// useGlobalVar();
// useCountDownLatch();
// useCyclicBarrier();
// 没想出来，但感觉应该可以的。
// useSemaphore();
// useSynchronized();
System.out.println("异步计算结果为：" + result);
System.out.println("使用时间：" + (System.currentTimeMillis() - start) + "ms");
}
static Integer result = 0;
static boolean finish = false;
static Object lock = new Object();
/**
* 使用Callable返回Future，获得新线程的返回值
* @throws InterruptedException
* @throws ExecutionException
*/
public static void useFuture() throws InterruptedException, ExecutionException {
Future<Integer> future = Executors.newCachedThreadPool().submit(new Callable<Integer>() {
@Override
public Integer call() throws Exception {
System.out.println("返回运算结果：1");
return 1;
}
});
result = future.get();
}
/**
* 将Callable包装秤FutureTask，异步完成任务，返回返回值。
* @throws InterruptedException
* @throws ExecutionException
*/
public static void useFutureTask() throws InterruptedException, ExecutionException {
FutureTask<Integer> task = new FutureTask<>(new Callable<Integer>() {
@Override
public Integer call() throws Exception {
return 1;
}
});
//使用Thread
// new Thread(task).start();;
// result = task.get();
//使用线程池
Executors.newCachedThreadPool().submit(task);
result = task.get();
}
/**
* 使用Java8新特性CompletableFuture异步获得计算结果，并返回计算结果。
*/
public static void useCompletableFuture() {
// CompletableFuture.supplyAsync(()->{return 1;}).thenApply(v -> result = v);
CompletableFuture.supplyAsync(()->{ return 1;}).thenAccept(v -> result = v);
}
/**
* 通过使用Object的wait，使主线程阻塞，当新线程完成任务后将主线程唤醒，返回计算结果。
* @throws InterruptedException
*/
public static void useObjectWait() throws InterruptedException {
new Thread(()->{
synchronized(lock) {
result = 1;
lock.notifyAll();
}
}) .start();
synchronized(lock) {
lock.wait();
}
}
/**
* 没想出来，使用Synchronized只能使两个线程先后进入同一代码块，却无法控制前后顺序，main先进入则无法获得新线程计算结果。
*/
public static void useSynchronized() {
new Thread(() -> {
addOrRead(Operation.ADD, 1);
}).start();
result = addOrRead(Operation.READ);
}
public synchronized static Integer addOrRead(Operation operation,Integer... num) {
System.out.println("thread:"+Thread.currentThread().getName()+" 进入代码");
switch(operation) {
case ADD :
Arrays.asList(num).stream().forEach((n)->{result += n;});
break;
case READ :
}
System.out.println("thread:"+Thread.currentThread().getName()+" 退出代码");
return result;
}
public enum Operation {
ADD,READ
}
/**
* 使用Lock的Condition，将主线程阻塞，当新线程完成计算后，唤醒主线程返回计算结果。
* @throws InterruptedException
*/
public static void useLock() throws InterruptedException {
Lock lock = new ReentrantLock();
Condition condition = lock.newCondition();
new Thread(()->{
lock.lock();
try {
result = 1;
condition.signalAll();
} finally {
lock.unlock();
}
}).start();
lock.lock();
try {
condition.await();
} finally {
lock.unlock();
}
}
/**
* 与Lock，object.wait() 类似，阻塞主线程，当新线程完成任务后，再唤醒主线程返回计算结果。
*/
public static void useLockSupport() {
Thread thread = Thread.currentThread();
new Thread(()->{
result = 1;
LockSupport.unpark(thread);
}).start();
LockSupport.park();
}
/**
* 使用Thread.join()，主线程只有在新线程完成之后才能返回。
* @throws InterruptedException
*/
public static void useJoin() throws InterruptedException {
Thread thread = new Thread(() -> {
result = 1;
});
thread.start();
thread.join();
}
/**
* 没想出来，与Synchronized类似，无法控制使用信号量的先后顺序。
*/
public static void useSemaphore() {
}
/**
* 使用CountDownLatch工具类，只有当countDownLatch的数量countDown到0，主线程才可继续运行。
* @throws InterruptedException
*/
public static void useCountDownLatch() throws InterruptedException {
CountDownLatch countDownLatch = new CountDownLatch(1);
new Thread(() -> {
result = 1;
countDownLatch.countDown();
}).start();;
countDownLatch.await();
}
/**
* 使用CyclicBarrier工具类，当主线程与新线程都await，cyclicBarrier的等待数为2，则唤醒所有线程。
* @throws InterruptedException
* @throws BrokenBarrierException
*/
public static void useCyclicBarrier() throws InterruptedException, BrokenBarrierException {
CyclicBarrier cyclicBarrier = new CyclicBarrier(2);
new Thread(() -> {
result = 1;
try {
cyclicBarrier.await();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (BrokenBarrierException e) {
e.printStackTrace();
}
}).start();;
cyclicBarrier.await();
}
/**
* 使用一共享变量表示新线程是否计算完毕，主线程轮训当发现变量表示新线程已计算完毕，则返回。
*/
public static void useGlobalVar() {
new Thread(() -> {
result = 1;
finish = true;
}).start();;
while(true) {
if (finish) {
break;
}
}
}
}