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这篇文章主要讲解了“Java线程池的使用实例”,文中的讲解内容简单清晰,易于学习与理解,下面请大家跟着小编的思路慢慢深入,一起来研究和学习“Java线程池的使用实例”吧!
TestThreadPool.java
import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class TestThreadPool { public static void main(String[] args) { long startTime = System.currentTimeMillis(); //获取开始时间 ExecutorService fixedThreadPool = Executors.newFixedThreadPool(5);//设置线程池的最大线程数 for (int i = 0; i < 10; i++) { final int index = i;//一般多线程并发都用final fixedThreadPool.execute(new Runnable() { public void run() { System.out.println(index + " " + Thread.currentThread().getName()); } }); } long endTime = System.currentTimeMillis(); //获取结束时间 System.out.println("程序运行时间:" + (endTime - startTime) + "ms"); } }
输出结果: (当然输出结果不是固定的,不过线程数一定不会超过5个)
可以看到 Thread.currentThread().getName() 拿到的name只有5种,说明最大线程数控制在 5 个
工作队列用了LinkedBlockingQueue ,无界队列,当任务多而线程数少时,任务会存在队列里,容易内存溢出。
TestThreadPool1.java
import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class TestThreadPool1 { public static void main(String[] args) { ExecutorService cachedThreadPool = Executors.newCachedThreadPool(); for (int i = 0; i < 10000; i++) { final int index = i; cachedThreadPool.execute(new Runnable() { public void run() { System.out.println(index + " " + Thread.currentThread().getName()); } }); } } }
输出结果的 Thread.currentThread().getName() 拿到的name有一两千种(当然不同环境和配置的机器的结果最大线程数是不同的)
工作队列使用SynchronousQueue同步队列。会根据任务数创建线程,数量太大容易导致cpu使用率100% 99%
TestThreadPool2.java
import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class TestThreadPool2 { public static void main(String[] args) { ExecutorService singleThreadExecutor = Executors.newSingleThreadExecutor(); for (int i = 0; i < 10000; i++) { final int index = i; singleThreadExecutor.execute(new Runnable() { public void run() { System.out.println(index + " " + Thread.currentThread().getName()); } }); } } }
输出结果:无论循环100次还是100000次,输出结果Thread.currentThread().getName()的值都会是
pool-1-thread-1
TestThreadPool3.java
import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class TestThreadPool3 { public static void main(String[] args) { ExecutorService singleThreadExecutor = Executors.newCachedThreadPool(); for (int i = 0; i < 10; i++) { final int index = i; singleThreadExecutor.execute(new Runnable() { public void run() { try { while(true) { System.out.println(index + " " + Thread.currentThread().getName()); Thread.sleep(10 * 1000); } } catch (InterruptedException e) { e.printStackTrace(); } } }); } } }
输出结果:每隔10s就会输出10行结果
**使用 ScheduledExecutorService 的 scheduleAtFixedRate方法可以设置延时和执行间隔
scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit)
Creates and executes a periodic action that becomes enabled first after the given initial delay, and subsequently with the given period; that is executions will commence after initialDelay then initialDelay+period, then initialDelay + 2 * period, and so on.
意思是创建并执行一个在给定初始延迟后首次启用的定期操作,后续操作具有给定的周期;也就是将在 initialDelay 后开始执行,然后在 initialDelay+period 后执行,接着在 initialDelay + 2 * period 后执行,依此类推。
TestThreadPool4.java
import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; public class TestThreadPool4 { public static void main(String[] args) { ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5); System.out.println(System.currentTimeMillis()); scheduledThreadPool.scheduleAtFixedRate(new Runnable() { public void run() { System.out.println(System.currentTimeMillis()); } }, 5, 10, TimeUnit.SECONDS); } }
从输出结果可以看出,延时5s后每隔10s会输出一次当前时间。
**使用ScheduledExecutorService的schedule可以设置首次执行延时
schedule(Runnable command, long delay, TimeUnit unit)
Creates and executes a one-shot action that becomes enabled after the given delay.
创建并执行在给定延迟后启用的一次性操作。
TestThreadPool5.java
import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; public class TestThreadPool5 { public static void main(String[] args) { ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5); for (int i = 0; i < 10; i++) { final int index = i; scheduledThreadPool.schedule(new Runnable() { public void run() { System.out.println(index + " " + Thread.currentThread().getName()); } }, 3, TimeUnit.SECONDS); } } }
输出结果:运行3s后会输出10行结果,而不会每隔3s输出一行。
感谢各位的阅读,以上就是“Java线程池的使用实例”的内容了,经过本文的学习后,相信大家对Java线程池的使用实例这一问题有了更深刻的体会,具体使用情况还需要大家实践验证。这里是亿速云,小编将为大家推送更多相关知识点的文章,欢迎关注!
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