[英]How to set priority of java.util.Timer
如何在Java中設置計時器的線程優先級? 這是我在我正在處理的項目中找到的代碼,但我認為它不起作用:
public static Timer createNamedTimer(boolean isDaemon,
final String threadName, final int priority) {
Timer timer = new Timer(isDaemon);
timer.schedule(new TimerTask() {
public void run() {
Thread.currentThread().setName("TimerThread: " + threadName);
Thread.currentThread().setPriority(priority);
}
}, 0);
return timer;
}
定時器的AFAIK唯一可以更改優先級的方法就是您執行的方法。
如果需要更好的選擇,可以使用ThreadFactory創建線程並設置其優先級。
class SimpleThreadFactory implements ThreadFactory {
private int threadPriority;
public Thread newThread(Runnable r) {
Thread t = new Thread(r);
t.setPriority(threadPriority);
return t;
}
}
然后,您可以將工廠傳遞給Java的Executors框架以執行所需的操作,恕我直言,這將是一種更好的方法。
為什么我說這將是更好的方法?
Timer類的JavaDoc提到ScheduledThreadPoolExecutor
並指出,該類實際上是Timer/TimerTask
組合的更通用的替代品
建議的解決方案不太適合重復多次的任務,因為在調用之間,共享同一線程的另一個任務可能已將優先級調整為其他任務。 因此,對於重復任務,您必須每次在執行時設置優先級。 沒有新的Executors
框架就存在此潛在問題。
一種解決方案是創建一個包裝類,為您做准備工作以確保一致性。 例如:
AnyClass.java:
private static void exampleUsage()
{
try { launchHighPriorityTask(() -> System.out.println("What a fancy task.")).join(); }
catch (Throwable ignored) {}
}
private static Thread launchMaxPriorityTask(Runnable task)
{
final Thread customThread = new Thread(new Task("MaxPriority", Thread.MAX_PRIORITY, task));
customThread.start();
return customThread;
}
Task.java:
public class Task implements Runnable
{
private final String name;
private final int priority;
private final Runnable task;
public Task(String name, int priority, Runnable task)
{
if (null == task) throw new NullPointerException("no task provided");
this.name = name; this.priority = priority; this.task = task;
}
/**
* run() is made final here to prevent any deriving classes
* accidentally ruining the expected behavior
*/
@Override public final void run()
{
final Thread thread = Thread.currentThread();
// cache the current state to restore settings and be polite
final String prevName = thread.getName();
final int prevPriority = thread.getPriority();
// set our thread's config
thread.setName(name);
thread.setPriority(priority);
try { task.run(); } catch (Throwable ignored) {}
// restore previous thread config
thread.setPriority(prevPriority);
thread.setName(prevName);
}
}
這自然是這種設置可以完成的極簡示例。
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