java并发编程（二）-休眠、优先级

续接java并发编程（一），本篇文章主要分析线程休眠、优先级、让步，例子沿用对《java编程思想》练习题进行改编。

休眠

练习一：创建一个任务，它休眠1至10秒之间的随机数量的时间，然后显示它的休眠时间并退出。创建并运行一定数量的这种任务

package twentyoneThread;

import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

class ExcFive implements Runnable {
private final int maxSleepTime = 10;
private int sleepTime;
private static int taskCount = 0;
private final int id = taskCount++;
private Random random=new Random();
//返回休眠时间
public String Status() {
return "#" + id + " thread sleep " + sleepTime + "secends";

}

public ExcFive() {
sleepTime = random.nextInt(maxSleepTime)+1;//生成随机休眠数

}

@Override
public void run() {
try {
TimeUnit.MILLISECONDS.sleep(sleepTime);//推荐休眠时间的写法
System.out.println(Status());
Thread.yield();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
}

public class TestExcFive {
public static void main(String[] args) {
ExecutorService exes = Executors.newCachedThreadPool();
for (int i = 0; i < 5; i++) {
exes.execute(new ExcFive());

}
exes.shutdown();
}
}

输出式样：

#4 thread sleep 2secends
#2 thread sleep 7secends
#3 thread sleep 7secends
#1 thread sleep 10secends
#0 thread sleep 9secends

优先级

线程优先级将线程的重要性传递给了调度器。然而，这并不是意味着优先权较低的线程将得不到执行（也就是说，优先权不会导致死锁）。较低的优先级的线程仅仅是执行的频率较低。

package twentyoneThread;

import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

class ExcSix implements Runnable {
private int countDown = 3;
private int priority;
private static int taskCount = 0;
private final int id = taskCount++;

public String Status() {
return  Thread.currentThread()+"#" + id +"priortity=" +Thread.currentThread().getPriority()+"countDown="+countDown;

}

public ExcSix(int priortity) {

this.priority= priortity;
}

@Override
public void run() {
Thread.currentThread().setPriority(priority);
while (countDown-- > 0) {
System.out.println(Status());
Thread.yield();
}

}

}

public class TestExcSix {
public static void main(String[] args) {
ExecutorService exes = Executors.newCachedThreadPool();
for (int i = 0; i < 5; i++) {
exes.execute(new ExcSix(Thread.MIN_PRIORITY));
exes.execute(new ExcSix(Thread.MAX_PRIORITY));

}

exes.shutdown();
}
}

输出式样：

Thread[pool-1-thread-2,10,main]#1priortity=10countDown=2
Thread[pool-1-thread-4,10,main]#3priortity=10countDown=2
Thread[pool-1-thread-2,10,main]#1priortity=10countDown=1
Thread[pool-1-thread-4,10,main]#3priortity=10countDown=1
Thread[pool-1-thread-2,10,main]#1priortity=10countDown=0
Thread[pool-1-thread-4,10,main]#3priortity=10countDown=0
Thread[pool-1-thread-3,1,main]#2priortity=1countDown=2
Thread[pool-1-thread-5,1,main]#4priortity=1countDown=2
Thread[pool-1-thread-7,1,main]#6priortity=1countDown=2
Thread[pool-1-thread-9,1,main]#8priortity=1countDown=2
Thread[pool-1-thread-1,1,main]#0priortity=1countDown=2
Thread[pool-1-thread-3,1,main]#2priortity=1countDown=1
Thread[pool-1-thread-6,10,main]#5priortity=10countDown=2
Thread[pool-1-thread-5,1,main]#4priortity=1countDown=1
Thread[pool-1-thread-7,1,main]#6priortity=1countDown=1
Thread[pool-1-thread-9,1,main]#8priortity=1countDown=1
Thread[pool-1-thread-8,10,main]#7priortity=10countDown=2
Thread[pool-1-thread-6,10,main]#5priortity=10countDown=1
Thread[pool-1-thread-8,10,main]#7priortity=10countDown=1
Thread[pool-1-thread-3,1,main]#2priortity=1countDown=0
Thread[pool-1-thread-1,1,main]#0priortity=1countDown=1
Thread[pool-1-thread-9,1,main]#8priortity=1countDown=0
Thread[pool-1-thread-7,1,main]#6priortity=1countDown=0
Thread[pool-1-thread-5,1,main]#4priortity=1countDown=0
Thread[pool-1-thread-6,10,main]#5priortity=10countDown=0
Thread[pool-1-thread-8,10,main]#7priortity=10countDown=0
Thread[pool-1-thread-1,1,main]#0priortity=1countDown=0
Thread[pool-1-thread-10,10,main]#9priortity=10countDown=2
Thread[pool-1-thread-10,10,main]#9priortity=10countDown=1
Thread[pool-1-thread-10,10,main]#9priortity=10countDown=0

总结

《java编程思想》里面关于线程的讲解很详细，篇幅较长，涉及的知识点也多，把里面的练习题都梳理一篇花费的时间也蛮久，太急切于梳理线程很可能会觉得枯燥、无味，坚持不下去。所以以后有条件，每天写一篇关于线程的理解，同时工作、学习中遇到的其它的问题都会试着去用博客的形式记录下来。对于写博客我自己还是一个新手，不是很适应，往往一篇很简短的文章自己都要写好久，也不会表达自己的感想。希望从今天开始自己以后每天坚持写博客，记录学习的点滴。