高效并发

public class MyRunnable implements Runnable {
public void run() {
    // ...
    }
}
public static void main(String[] args) {
    MyRunnable instance = new MyRunnable();
    Thread thread = new Thread(instance);
    thread.start();
}

public class MyCallable implements Callable<Integer> {
        public Integer call() {
        return 123;
    }
}
public static void main(String[] args) throws ExecutionException, InterruptedException {
    MyCallable mc = new MyCallable();
    FutureTask<Integer> ft = new FutureTask<>(mc);
    Thread thread = new Thread(ft);
    thread.start();
    System.out.println(ft.get());
}

public static void main(String[] args) {
    ExecutorService executorService = Executors.newCachedThreadPool();
    for (int i = 0; i < 5; i++) {
        executorService.execute(new MyRunnable());
    }
    executorService.shutdown();
}

public static void main(String[] args) {
    Thread thread = new Thread(new MyRunnable());
    thread.setDaemon(true);
}

public void run() {
    try {
    Thread.sleep(3000);
    } catch (InterruptedException e) {
    e.printStackTrace();
}

public void run() {
    Thread.yield();
}

public class InterruptExample {
    private static class MyThread1 extends Thread {
        @Override
        public void run() {
            try {
                Thread.sleep(2000);
                System.out.println("Thread run");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
         }
    }
}

public static void main(String[] args) throws InterruptedException {
    Thread thread1 = new MyThread1();
    thread1.start();
    thread1.interrupt();
    System.out.println("Main run");
}

Main run
java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)
at InterruptExample.lambda$main$0(InterruptExample.java:5)
at InterruptExample$$Lambda$1/713338599.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)

public class InterruptExample {
    private static class MyThread2 extends Thread {
    @Override
        public void run() {
            while (!interrupted()) {
            // ..
            }
            System.out.println("Thread end");
        }
    }
}

public static void main(String[] args) throws InterruptedException {
    Thread thread2 = new MyThread2();
    thread2.start();
    thread2.interrupt();
}
Thread end

public static void main(String[] args) {
    ExecutorService executorService = Executors.newCachedThreadPool();
    executorService.execute(() -> {
        try {
            Thread.sleep(2000);
            System.out.println("Thread run");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    });
    executorService.shutdownNow();
    System.out.println("Main run");
}

Main run
java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)
at ExecutorInterruptExample.lambda$main$0(ExecutorInterruptExample.java:9)
at ExecutorInterruptExample$$Lambda$1/1160460865.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

Future<?> future = executorService.submit(() -> {
    // ..
});
future.cancel(true);

public void func() {
    synchronized (this) {
    // ...
    }
}

public class SynchronizedExample {
    public void func1() {
        synchronized (this) {
        for (int i = 0; i < 10; i++) {
                System.out.print(i + " ");
            }
        }
    }
}

public static void main(String[] args) {
    SynchronizedExample e1 = new SynchronizedExample();
    ExecutorService executorService = Executors.newCachedThreadPool();
    executorService.execute(() -> e1.func1());
    executorService.execute(() -> e1.func1());
}

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9

public static void main(String[] args) {
    SynchronizedExample e1 = new SynchronizedExample();
    SynchronizedExample e2 = new SynchronizedExample();
    ExecutorService executorService = Executors.newCachedThreadPool();
    executorService.execute(() -> e1.func1());
    executorService.execute(() -> e2.func1());
}

0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9

public synchronized void func () {
    // ...
}

public void func() {
    synchronized (SynchronizedExample.class) {
        // ...
    }
}

public class SynchronizedExample {
    public void func2() {
        synchronized (SynchronizedExample.class) {
                for (int i = 0; i < 10; i++) {
                System.out.print(i + " ");
            }
        }
    }
}

public static void main(String[] args) {
    SynchronizedExample e1 = new SynchronizedExample();
    SynchronizedExample e2 = new SynchronizedExample();
    ExecutorService executorService = Executors.newCachedThreadPool();
    executorService.execute(() -> e1.func2());
    executorService.execute(() -> e2.func2());
}

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public synchronized static void fun() {
    // ...
}

public class LockExample {
    private Lock lock = new ReentrantLock();
    public void func() {
        lock.lock();
        try {
            for (int i = 0; i < 10; i++) {
                System.out.print(i + " ");
               }
        } finally {
            lock.unlock(); // 确保释放锁，从而避免发生死锁。
        }
    }
}

public static void main(String[] args) {
    LockExample lockExample = new LockExample();
    ExecutorService executorService = Executors.newCachedThreadPool();
    executorService.execute(() -> lockExample.func());
    executorService.execute(() -> lockExample.func());
}

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9

// 支持中断的 API
void lockInterruptibly() throws InterruptedException;
// 支持超时的 API
boolean tryLock(long time, TimeUnit unit)throws InterruptedException;
// 支持非阻塞获取锁的 API
boolean tryLock();

public class JoinExample {
    private class A extends Thread {
         @Override
        public void run() {
        System.out.println("A");
        }
    }
    private class B extends Thread {
        private A a;
        B(A a) {
        this.a = a;
        }
        @Override
        public void run() {
            try {
                    a.join();
            } catch (InterruptedException e) {
                   e.printStackTrace();
            }
            System.out.println("B");
        }
    }
    public void test() {
        A a = new A();
        B b = new B(a);
        b.start();
        a.start();
    }
}

public static void main(String[] args) {
    JoinExample example = new JoinExample();
    example.test();
}

A
B

public class WaitNotifyExample {
    public synchronized void before() {
        System.out.println("before");
        notifyAll();
    }
    public synchronized void after() {
        try {
            wait();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("after");
    }
}

public static void main(String[] args) {
    ExecutorService executorService = Executors.newCachedThreadPool();
    WaitNotifyExample example = new WaitNotifyExample();
    executorService.execute(() -> example.after());
    executorService.execute(() -> example.before());
}

before
after

public class AwaitSignalExample {
    private Lock lock = new ReentrantLock();
    private Condition condition = lock.newCondition();
    public void before() {
        lock.lock();
        try {
            System.out.println("before");
            condition.signalAll();
        } finally {
             lock.unlock();
        }
    }
    public void after() {
        lock.lock();
        try {
            condition.await();
            System.out.println("after");
        } catch (InterruptedException e) {
               e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}

public static void main(String[] args) {
    ExecutorService executorService = Executors.newCachedThreadPool();
    AwaitSignalExample example = new AwaitSignalExample();
    executorService.execute(() -> example.after());
    executorService.execute(() -> example.before());
}

before
after

public class CountdownLatchExample {
    public static void main(String[] args) throws InterruptedException {
        final int totalThread = 10;
        CountDownLatch countDownLatch = new CountDownLatch(totalThread);
        ExecutorService executorService = Executors.newCachedThreadPool();
        for (int i = 0; i < 12; i++) {
            executorService.execute(() -> {
                System.out.print("run..");
                countDownLatch.countDown();
            });
        }
        countDownLatch.await();
        System.out.println("end");
        executorService.shutdown();
    }
}

run..run..run..run..run..run..run..run..run..run..run..end
run..

    import java.util.concurrent.CountDownLatch;  
      
    public class Race {  
      
        public static void main(String[] args) {  
            final int num = 5;  
            final CountDownLatch begin = new CountDownLatch(1);  
            final CountDownLatch end = new CountDownLatch(num);  
      
            for (int i = 0; i < num; i++) {  
                new Thread(new AWorker(i, begin, end)).start();  
            }  
      
            // judge prepare...  
            try {  
                Thread.sleep((long) (Math.random() * 5000));  
            } catch (InterruptedException e1) {  
                e1.printStackTrace();  
            }  
      
            System.out.println("judge say : run !");  
            begin.countDown();  
            long startTime = System.currentTimeMillis();  
      
            try {  
                end.await();  
            } catch (InterruptedException e) {  
                e.printStackTrace();  
            } finally {  
                long endTime = System.currentTimeMillis();  
                System.out.println("judge say : all arrived !");  
                System.out.println("spend time: " + (endTime - startTime));  
            }  
      
        }  
      
    }  
      
    class AWorker implements Runnable {  
        final CountDownLatch begin;  
        final CountDownLatch end;  
        final int id;  
      
        public AWorker(final int id, final CountDownLatch begin,  
                final CountDownLatch end) {  
            this.id = id;  
            this.begin = begin;  
            this.end = end;  
        }  
      
        @Override  
        public void run() {  
            try {  
                System.out.println(this.id + " ready !");  
                begin.await();  
                // run...  
                Thread.sleep((long) (Math.random() * 10000));  
            } catch (Throwable e) {  
                e.printStackTrace();  
            } finally {  
                System.out.println(this.id + " arrived !");  
                end.countDown();  
            }  
        }  
      
    } 

public CyclicBarrier(int parties, Runnable barrierAction) {
    if (parties <= 0) throw new IllegalArgumentException();
    this.parties = parties;
    this.count = parties;
    this.barrierCommand = barrierAction;
}
public CyclicBarrier(int parties) {
    this(parties, null);
}

public class CyclicBarrierExample {
    public static void main(String[] args) {
        final int totalThread = 10;
        CyclicBarrier cyclicBarrier = new CyclicBarrier(totalThread);
        ExecutorService executorService = Executors.newCachedThreadPool();
        for (int i = 0; i < 12; i++) {
            executorService.execute(() -> {
                System.out.print("before..");
                try {
                    cyclicBarrier.await();
                } catch (InterruptedException | BrokenBarrierException e) {
                    e.printStackTrace();
                }
                System.out.print("after..");
            });
        }
        executorService.shutdown();
    }
}

before..before..before..before..before..before..before..before..before..before..before..after..before..after..after..after..after..after..after..after..after..after..

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
 
public class Beer {
 
    public static void main(String[] args) {
        final int count = 5;
        final CyclicBarrier barrier = new CyclicBarrier(count, new Runnable() {
            @Override
            public void run() {
                System.out.println("drink beer!");
            }
        });
 
        // they do not have to start at the same time...
        for (int i = 0; i < count; i++) {
            new Thread(new Worker(i, barrier)).start();
        }
    }
 
}
 
class Worker implements Runnable {
    final int id;
    final CyclicBarrier barrier;
 
    public Worker(final int id, final CyclicBarrier barrier) {
        this.id = id;
        this.barrier = barrier;
    }
 
    @Override
    public void run() {
        try {
            System.out.println(this.id + "starts to run !");
            Thread.sleep((long) (Math.random() * 10000));
            System.out.println(this.id + "arrived !");
            this.barrier.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (BrokenBarrierException e) {
            e.printStackTrace();
        }
    }
}

public class SemaphoreExample {
    public static void main(String[] args) {
        final int clientCount = 3;
        final int totalRequestCount = 10;
        Semaphore semaphore = new Semaphore(clientCount);
        ExecutorService executorService = Executors.newCachedThreadPool();
        for (int i = 0; i < totalRequestCount; i++) {
            executorService.execute(()->{
                try {
                    semaphore.acquire();
                    System.out.print(semaphore.availablePermits() + " ");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {
                    semaphore.release();
                }
            });
        }
        executorService.shutdown();
    }
}

2 2 2 2 2 2 1 2 2 2 

public class FutureTask<V> implements RunnableFuture<V>
public interface RunnableFuture<V> extends Runnable, Future<V>

public class FutureTaskExample {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        FutureTask<Integer> futureTask = new FutureTask<Integer>(new Callable<Integer>() {
            @Override
            public Integer call() throws Exception {
                int result = 0;
                for (int i = 0; i < 100; i++) {
                    Thread.sleep(10);
                    result += i;
                }
                return result;
            }
        });
        Thread computeThread = new Thread(futureTask);
        computeThread.start();
        Thread otherThread = new Thread(() -> {
            System.out.println("other task is running...");
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("other tash is over....");
        });
        otherThread.start();
        System.out.println(futureTask.get());
    }
}

other task is running...
other tash is over....
4950

public class ProducerConsumer {
    private static BlockingQueue<String> queue = new ArrayBlockingQueue<>(5);
    private static class Producer extends Thread {
        @Override
        public void run() {
            try {
                queue.put("product");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.print("produce..");
        }
    }
    private static class Consumer extends Thread {
        @Override
        public void run() {
            try {
                String product = queue.take();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.print("consume..");
        }
    }

    public static void main(String[] args) {
        for (int i = 0; i < 2; i++) {
            Producer producer = new Producer();
            producer.start();
        }
        for (int i = 0; i < 5; i++) {
            Consumer consumer = new Consumer();
            consumer.start();
        }
        for (int i = 0; i < 3; i++) {
            Producer producer = new Producer();
            producer.start();
        }
    }
}

produce..produce..consume..consume..produce..consume..produce..consume..produce..consume..

public class ForkJoinExample extends RecursiveTask<Integer> {
    private final int threshold = 5;
    private int first;
    private int last;

    public ForkJoinExample(int first, int last) {
        this.first = first;
        this.last = last;
    }

    @Override
    protected Integer compute() {
        int result = 0;
        if (last - first <= threshold) {
// 任务足够小则直接计算
            for (int i = first; i <= last; i++) {
                result += i;
            }
        } else {
// 拆分成小任务
            int middle = first + (last - first) / 2;
            ForkJoinExample leftTask = new ForkJoinExample(first, middle);
            ForkJoinExample rightTask = new ForkJoinExample(middle + 1, last);
            leftTask.fork();
            rightTask.fork();
            result = leftTask.join() + rightTask.join();
        }
        return result;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        ForkJoinExample example = new ForkJoinExample(1, 10000);
        ForkJoinPool forkJoinPool = new ForkJoinPool();
        Future result = forkJoinPool.submit(example);
        System.out.println(result.get());
    }
}

public class ForkJoinPool extends AbstractExecutorService

public class ThreadUnsafeExample {
    private int cnt = 0;
    public void add() {
        cnt++;
    }
    public int get() {
        return cnt;
    }

    public static void main(String[] args) throws InterruptedException {
        final int threadSize = 1000;
        ThreadUnsafeExample example = new ThreadUnsafeExample();
        final CountDownLatch countDownLatch = new CountDownLatch(threadSize);
        ExecutorService executorService = Executors.newCachedThreadPool();
        for (int i = 0; i < threadSize; i++) {
            executorService.execute(() -> {
                example.add();
                countDownLatch.countDown();
            });
        }
        countDownLatch.await();
        executorService.shutdown();
        System.out.println(example.get());
    }
}

996

public class AtomicExample {
    private AtomicInteger cnt = new AtomicInteger();
    public void add() {
        cnt.incrementAndGet();
    }
    public int get() {
        return cnt.get();
    }

    public static void main(String[] args) throws InterruptedException {
        final int threadSize = 1000;
        AtomicExample example = new AtomicExample(); // 只修改这条语句
        final CountDownLatch countDownLatch = new CountDownLatch(threadSize);
        ExecutorService executorService = Executors.newCachedThreadPool();
        for (int i = 0; i < threadSize; i++) {
            executorService.execute(() -> {
                example.add();
                countDownLatch.countDown();
            });
        }
        countDownLatch.await();
        executorService.shutdown();
        System.out.println(example.get());
    }
}

1000

public class AtomicSynchronizedExample {
    private int cnt = 0;
    public synchronized void add() {
        cnt++;
    }
    public synchronized int get() {
        return cnt;
    }

    public static void main(String[] args) throws InterruptedException {
        final int threadSize = 1000;
        AtomicSynchronizedExample example = new AtomicSynchronizedExample();
        final CountDownLatch countDownLatch = new CountDownLatch(threadSize);
        ExecutorService executorService = Executors.newCachedThreadPool();
        for (int i = 0; i < threadSize; i++) {
            executorService.execute(() -> {
                example.add();
                countDownLatch.countDown();
            });
        }
        countDownLatch.await();
        executorService.shutdown();
        System.out.println(example.get());
    }
}

1000

public class ImmutableExample {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<>();
        Map<String, Integer> unmodifiableMap = Collections.unmodifiableMap(map);
        unmodifiableMap.put("a", 1);
    }
}
Exception in thread "main" java.lang.UnsupportedOperationException
    at java.util.Collections$UnmodifiableMap.put(Collections.java:1457)
    at ImmutableExample.main(ImmutableExample.java:9)

public V put(K key, V value) {
    throw new UnsupportedOperationException();
}

private AtomicInteger cnt = new AtomicInteger();
public void add() {
    cnt.incrementAndGet();
}

public final int incrementAndGet() {
    return unsafe.getAndAddInt(this, valueOffset, 1) + 1;
}

public final int getAndAddInt(Object var1, long var2, int var4) {
    int var5;
    do {
           var5 = this.getIntVolatile(var1, var2);
    } while(!this.compareAndSwapInt(var1, var2, var5, var5 + var4));
    return var5;
}

public class StackClosedExample {
    public void add100() {
        int cnt = 0;
        for (int i = 0; i < 100; i++) {
        cnt++;
        }
        System.out.println(cnt);
    }
}

public static void main(String[] args) {
    StackClosedExample example = new StackClosedExample();
    ExecutorService executorService = Executors.newCachedThreadPool();
    executorService.execute(() -> example.add100());
    executorService.execute(() -> example.add100());
    executorService.shutdown();
}

100
100

public class ThreadLocalExample {
    public static void main(String[] args) {
        ThreadLocal threadLocal = new ThreadLocal();
        Thread thread1 = new Thread(() -> {
            threadLocal.set(1);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(threadLocal.get());
            threadLocal.remove();
        });
        Thread thread2 = new Thread(() -> {
            threadLocal.set(2);
            threadLocal.remove();
        });
        thread1.start();
        thread2.start();
    }
}

public class ThreadLocalExample1 {
    public static void main(String[] args) {
    ThreadLocal threadLocal1 = new ThreadLocal();
    ThreadLocal threadLocal2 = new ThreadLocal();
    Thread thread1 = new Thread(() -> {
        threadLocal1.set(1);
        threadLocal2.set(1);
    });
    Thread thread2 = new Thread(() -> {
        threadLocal1.set(2);
        threadLocal2.set(2);
    });
    thread1.start();
    thread2.start();
    }
}

/* ThreadLocal values pertaining to this thread. This map is maintained
* by the ThreadLocal class. */
ThreadLocal.ThreadLocalMap threadLocals = null;

public void set(T value) {
    Thread t = Thread.currentThread();
    ThreadLocalMap map = getMap(t);
    if (map != null)
           map.set(this, value);
    else
        createMap(t, value);
}

public T get() {
    Thread t = Thread.currentThread();
    ThreadLocalMap map = getMap(t);
    if (map != null) {
        ThreadLocalMap.Entry e = map.getEntry(this);
        if (e != null) {
            @SuppressWarnings("unchecked")
            T result = (T)e.value;
            return result;
        }
    }
    return setInitialValue();
}

public static String concatString(String s1, String s2, String s3) {
    return s1 + s2 + s3;
}

public static String concatString(String s1, String s2, String s3) {
    StringBuffer sb = new StringBuffer();
    sb.append(s1);
    sb.append(s2);
    sb.append(s3);
    return sb.toString();
}