[英]How to set priority of java.util.Timer
如何在Java中设置计时器的线程优先级? 这是我在我正在处理的项目中找到的代码,但我认为它不起作用:
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;
}
定时器的AFAIK唯一可以更改优先级的方法就是您执行的方法。
如果需要更好的选择,可以使用ThreadFactory创建线程并设置其优先级。
class SimpleThreadFactory implements ThreadFactory {
private int threadPriority;
public Thread newThread(Runnable r) {
Thread t = new Thread(r);
t.setPriority(threadPriority);
return t;
}
}
然后,您可以将工厂传递给Java的Executors框架以执行所需的操作,恕我直言,这将是一种更好的方法。
为什么我说这将是更好的方法?
Timer类的JavaDoc提到ScheduledThreadPoolExecutor
并指出,该类实际上是Timer/TimerTask
组合的更通用的替代品
建议的解决方案不太适合重复多次的任务,因为在调用之间,共享同一线程的另一个任务可能已将优先级调整为其他任务。 因此,对于重复任务,您必须每次在执行时设置优先级。 没有新的Executors
框架就存在此潜在问题。
一种解决方案是创建一个包装类,为您做准备工作以确保一致性。 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);
}
}
这自然是这种设置可以完成的极简示例。
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