优先级高的线程在竞争资源时会更有优势，更可能抢占资源，只是一个概率问题；

线程的优先级调度和底层操作系统有密切的关系，在各个平台上表现不一，并且无法精准控制，因此在要求严格的场合，需要开发者在应用层解决线程调度问题；

线程优先级用内置3个静态标量表示：

/**
 * The minimum priority that a thread can have.
 */
public final static int MIN_PRIORITY = 1;
/**
 * The default priority that is assigned to a thread.
 */
public final static int NORM_PRIORITY = 5;
/**
 * The maximum priority that a thread can have.
 */
public final static int MAX_PRIORITY = 10;

虽然设置最高和最低优先级，但真正执行结果不可预测：

public class ThreadPriorityDemo {
	public static class HighPriorityThread extends Thread {
		static int count = 0;
		@Override
		public void run() {
			while (true) {
				synchronized (ThreadPriorityDemo.class) {
					count++;
					if (count > 10000000) {
						System.out.println("HighPriorityThread is complete." + System.currentTimeMillis());
						break;
					}
				}
			}
		}
	}
	public static class LowPriorityThread extends Thread {
		static int count = 0;
		@Override
		public void run() {
			while (true) {
				synchronized (ThreadPriorityDemo.class) {
					count++;
					if (count > 10000000) {
						System.out.println("LowPriorityThread is complete." + System.currentTimeMillis());
						break;
					}
				}
			}
		}
	}
	public static void main(String[] args) {
		Thread high = new HighPriorityThread();
		Thread low = new LowPriorityThread();
		high.setPriority(Thread.MAX_PRIORITY);
		low.setPriority(Thread.MIN_PRIORITY);
		System.out.println("start:" + System.currentTimeMillis());
		high.start();
		low.start();
	}
}

console

start:1549722133524
LowPriorityThread is complete.1549722134435
HighPriorityThread is complete.1549722134440