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java threadpoolexecutor如何實現任務優先級

小樊
81
2024-11-16 23:25:59
欄目: 編程語言

在Java中,ThreadPoolExecutor 本身并不支持任務優先級。但是,你可以通過以下方法實現任務優先級:

  1. 使用 PriorityBlockingQueue 作為工作隊列:PriorityBlockingQueue 是一個支持優先級的阻塞隊列,它可以根據任務的優先級對任務進行排序。你可以創建一個自定義的任務類(實現 RunnableCallable 接口),并在其中定義一個優先級屬性。然后,將任務類作為參數傳遞給 PriorityBlockingQueue 的構造函數。
class PriorityTask<T extends Comparable<T>> implements Runnable, Comparable<PriorityTask<T>> {
    private T priority;
    private Runnable task;

    public PriorityTask(T priority, Runnable task) {
        this.priority = priority;
        this.task = task;
    }

    @Override
    public void run() {
        task.run();
    }

    @Override
    public int compareTo(PriorityTask<T> other) {
        return other.priority.compareTo(this.priority);
    }
}
  1. 創建一個自定義的 ThreadPoolExecutor:繼承 ThreadPoolExecutor 類,并重寫 newTaskFor 方法。在這個方法中,將任務包裝成一個 PriorityTask 對象,并將其提交給 PriorityBlockingQueue
class PriorityThreadPoolExecutor extends ThreadPoolExecutor {
    public PriorityThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
    }

    @Override
    protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
        if (callable instanceof PriorityCallable) {
            return new PriorityFutureTask<>((PriorityCallable<T>) callable);
        } else {
            throw new IllegalArgumentException("Callable must implement PriorityCallable");
        }
    }
}
  1. 創建一個支持優先級的任務類:實現 PriorityCallable 接口,該接口擴展了 Callable 接口并添加了一個 getPriority() 方法。
class PriorityFutureTask<T> extends FutureTask<T> implements Comparable<PriorityFutureTask<T>> {
    private final int priority;

    public PriorityFutureTask(Callable<T> callable) {
        super(callable);
        if (!(callable instanceof PriorityCallable)) {
            throw new IllegalArgumentException("Callable must implement PriorityCallable");
        }
        this.priority = ((PriorityCallable<T>) callable).getPriority();
    }

    @Override
    public int compareTo(PriorityFutureTask<T> other) {
        return Integer.compare(other.priority, this.priority);
    }
}
  1. 使用自定義的 PriorityThreadPoolExecutor 提交任務:
PriorityThreadPoolExecutor executor = new PriorityThreadPoolExecutor(3, 5, 60, TimeUnit.SECONDS, new PriorityBlockingQueue<>());
executor.submit(new PriorityTask<>(1, () -> {
    System.out.println("Task with priority 1 is running");
    return null;
}));
executor.submit(new PriorityTask<>(3, () -> {
    System.out.println("Task with priority 3 is running");
    return null;
}));
executor.shutdown();

這樣,PriorityThreadPoolExecutor 將根據任務的優先級對任務進行排序,優先級較高的任務將優先執行。

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