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Java Thread.join怎樣避免線程饑餓現(xiàn)象

小樊
81
2024-10-09 13:47:50
欄目: 編程語言

為了避免Java中的線程饑餓現(xiàn)象，您可以采取以下措施：

  1. 公平鎖：使用java.util.concurrent.locks.ReentrantLock的公平鎖模式。在創(chuàng)建鎖的時候，通過傳入true參數(shù)來聲明這是一個公平鎖。公平鎖會按照線程請求鎖的順序來分配，從而避免了線程饑餓。
import java.util.concurrent.locks.ReentrantLock;

public class FairLockExample {
    private final ReentrantLock fairLock = new ReentrantLock(true);

    public void doSomething() {
        fairLock.lock();
        try {
            // Do some work here
        } finally {
            fairLock.unlock();
        }
    }
}
  1. 使用java.util.concurrent.Semaphore信號量：信號量可以用來限制對共享資源的訪問。通過設置合適的許可數(shù)量，可以確保線程按照預期的順序執(zhí)行，從而避免線程饑餓。
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

public class SemaphoreExample {
    private final Semaphore semaphore = new Semaphore(3); // Allow 3 threads to access the resource concurrently

    public void doSomething() {
        try {
            semaphore.acquire();
            // Do some work here
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        } finally {
            semaphore.release();
        }
    }

    public static void main(String[] args) {
        ExecutorService executorService = Executors.newFixedThreadPool(10);
        SemaphoreExample example = new SemaphoreExample();

        for (int i = 0; i < 10; i++) {
            executorService.submit(() -> example.doSomething());
        }

        executorService.shutdown();
    }
}
  1. 使用java.util.concurrent.PriorityBlockingQueue優(yōu)先級隊列：優(yōu)先級隊列可以根據(jù)元素的自然順序或者自定義的比較器來對元素進行排序。這樣，高優(yōu)先級的線程將優(yōu)先執(zhí)行，從而避免了線程饑餓。
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.PriorityBlockingQueue;
import java.util.concurrent.TimeUnit;

class Task implements Runnable, Comparable<Task> {
    @Override
    public int compareTo(Task other) {
        // Define the priority order here (higher priority first)
        return Integer.compare(other.priority, this.priority);
    }

    @Override
    public void run() {
        // Do some work here
    }

    public int priority;
}

public class PriorityQueueExample {
    private final PriorityBlockingQueue<Task> taskQueue = new PriorityBlockingQueue<>();

    public void addTask(Task task) {
        taskQueue.add(task);
    }

    public void startProcessing() {
        ExecutorService executorService = Executors.newSingleThreadExecutor();

        executorService.submit(() -> {
            while (!taskQueue.isEmpty()) {
                try {
                    Task task = taskQueue.take();
                    task.run();
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }
        });

        executorService.shutdown();
    }

    public static void main(String[] args) throws InterruptedException {
        PriorityQueueExample example = new PriorityQueueExample();

        // Add tasks with different priorities
        example.addTask(new Task(3));
        example.addTask(new Task(1));
        example.addTask(new Task(2));

        example.startProcessing();
    }
}

通過使用這些方法，您可以有效地避免線程饑餓現(xiàn)象，確保所有線程都能公平地訪問共享資源。

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