ThreadPoolExecutor允许提供一个BlockingQueue来保存等待执行的任务。
查看结构图
我们需要关注的方法是offer(E),put(E),take()
newFixedThreadPool和newSingleThreadExecutor在默认情况下将使用一个无界的队列(LinkedBlockingQueue),如果所有线程都在执行任务，那么任务将在队列中等待，如果任务到达的速度大于线程执行的速度，造成的后果将是队列无限期增加。
更稳妥的管理策略是使用有界队列，如：ArrayBlockingQueue,有界的LinkedBlockingQueue,PriorityBlockingQueue.有界队列避免了资源耗尽的情况，但出现一个问题，队列填满后，新的任务该怎么办？使用拒绝策略。
JDK提供了几种不同的RejectedExecutionHandler实现，每种都是不同的饱和策略：AbortPolicy,CallerRunsPolicy,DiscardPolicy和DiscardOldestPolicy.
AbortPolicy 当任务添加到线程池中被拒绝时，它将抛出 RejectedExecutionException 异常。如下代码：
1 package cn.concurrent.executor;
2
3 import java.util.concurrent.*;
4
5 /**
6 * Created by spark on 17-9-24.
7 */
8 public class AbortPolicyDemo {
9
10 public static void main(String[] args) {
11 //初始化一个初始化容量大小为1，阻塞队列容量为1，maxmumPoolSize大小为1的线程池
12 ThreadPoolExecutor pool = new ThreadPoolExecutor(1, 1,
13 0, TimeUnit.SECONDS, new LinkedBlockingQueue<>(1));
14 //设置饱和策略为AbortPolicy---拒绝策略/**/,用户可以捕获这个异常
15 pool.setRejectedExecutionHandler(new ThreadPoolExecutor.AbortPolicy());
16 //创建线程执行
17 for (int i = 0; i < 5; i++) {
18 MyRunnable myRunnable = new MyRunnable();
19 pool.execute(myRunnable);
20 }
21 pool.shutdown();
22 }
23
24
25 static class MyRunnable implements Runnable {
26 @Override
27 public void run() {
28 System.err.println(Thread.currentThread().getId() + ":正在执行");
29 try {
30 Thread.sleep(300);
31 } catch (InterruptedException e) {
32 e.printStackTrace();
33 }
34 }
35 }
36 }
结果如下：
Exception in thread "main" java.util.concurrent.RejectedExecutionException: Task cn.concurrent.executor.AbortPolicyDemo$MyRunnable@1d44bcfa rejected from java.util.concurrent.ThreadPoolExecutor@266474c2[Running, pool size = 1, active threads = 1, queued tasks = 1, completed tasks = 0]
at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2066)
at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:830)
at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1379)
at cn.concurrent.executor.AbortPolicyDemo.main(AbortPolicyDemo.java:19)
10:正在执行
10:正在执行
抛出了RejectedExecutionException，由于饱和策略引起的。
如果修改代码如下：
1 package cn.concurrent.executor;
2
3 import java.util.concurrent.*;
4
5 /**
6 * Created by spark on 17-9-24.
7 */
8 public class AbortPolicyDemo {
9
10 public static void main(String[] args) {
11 //初始化一个初始化容量大小为1，阻塞队列容量为1，maxmumPoolSize大小为1的线程池
12 ThreadPoolExecutor pool = new ThreadPoolExecutor(1, 1,
13 0, TimeUnit.SECONDS, new LinkedBlockingQueue<>(1));
14 //设置饱和策略为AbortPolicy---拒绝策略/**/,用户可以捕获这个异常
15 pool.setRejectedExecutionHandler(new ThreadPoolExecutor.AbortPolicy());
16 //创建线程执行
17 for (int i = 0; i < 5; i++) {
18 try {
19 Thread.sleep(500);
20 } catch (InterruptedException e) {
21 e.printStackTrace();
22 }
23 MyRunnable myRunnable = new MyRunnable();
24 pool.execute(myRunnable);
25 }
26 pool.shutdown();
27 }
28
29
30 static class MyRunnable implements Runnable {
31 @Override
32 public void run() {
33 System.err.println(Thread.currentThread().getId() + ":正在执行");
34 try {
35 Thread.sleep(300);
36 } catch (InterruptedException e) {
37 e.printStackTrace();
38 }
39 }
40 }
41 }
执行结果为：
1 /usr/lib/jvm/java-1.8.0-openjdk-amd64/bin/java -javaagent:/usr/local/idea/lib/idea_rt.jar=43205:/usr/local/idea/bin -Dfile.encoding=UTF-8 -classpath /usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/charsets.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/cldrdata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/dnsns.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/icedtea-sound.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/jaccess.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/localedata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/nashorn.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunec.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunpkcs11.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/zipfs.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jce.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jsse.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/management-agent.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/resources.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/rt.jar:/home/spark/IdeaProjects/thread/thread/target/classes:/home/spark/.m2/repository/com/lmax/disruptor/3.3.2/disruptor-3.3.2.jar cn.concurrent.executor.AbortPolicyDemo
2 10:正在执行
3 10:正在执行
4 10:正在执行
5 10:正在执行
6 10:正在执行
7
8 Process finished with exit code 0
原因是：正好每一个线程都有足够的时间执行，因此有界阻塞队列不会填满，程序能够正常运行。
DiscardOldestPolicy 当任务添加到线程池中被拒绝时，线程池会放弃等待队列中最旧的未处理任务(抛弃下一个将被执行的任务)，然后将被拒绝的任务添加到等待队列中，如果队列是一个优先队列，那么抛弃最旧的策略就会抛弃优先级最高的任务，因此不要将两者在一起使用。如下代码：
1 package cn.concurrent.executor;
2
3 import java.util.concurrent.ArrayBlockingQueue;
4 import java.util.concurrent.ThreadPoolExecutor;
5 import java.util.concurrent.TimeUnit;
6
7 /**
8 * Created by spark on 17-9-24.
9 */
10 public class DiscardOledesrPolicy {
11
12 public static void main(String[] args) {
13
14 ThreadPoolExecutor pool = new ThreadPoolExecutor(1, 1, 0, TimeUnit.SECONDS,
15 new ArrayBlockingQueue
16 //设置饱和策略为DiscardOledestPolicy
17 pool.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardOldestPolicy());
18
19
20 for (int i = 0; i < 6; i++) {
21 MyRunnable myRunnable = new MyRunnable("this is " + i + " task");
22 pool.submit(myRunnable);
23 }
24 pool.shutdown();
25 }
26
27 static class MyRunnable implements Runnable {
28
29 private String name;
30
31 public MyRunnable(String name) {
32 this.name = name;
33 }
34
35 @Override
36 public void run() {
37 System.err.println(this.name + ": is running.");
38 try {
39 Thread.sleep(300);
40 } catch (InterruptedException e) {
41 e.printStackTrace();
42 }
43 }
44 }
45 }
结果如下：
/usr/lib/jvm/java-1.8.0-openjdk-amd64/bin/java -javaagent:/usr/local/idea/lib/idea_rt.jar=33258:/usr/local/idea/bin -Dfile.encoding=UTF-8 -classpath /usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/charsets.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/cldrdata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/dnsns.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/icedtea-sound.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/jaccess.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/localedata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/nashorn.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunec.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunpkcs11.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/zipfs.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jce.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jsse.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/management-agent.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/resources.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/rt.jar:/home/spark/IdeaProjects/thread/thread/target/classes:/home/spark/.m2/repository/com/lmax/disruptor/3.3.2/disruptor-3.3.2.jar cn.concurrent.executor.DiscardOledesrPolicy
this is 0 task: is running.
this is 5 task: is running.
Process finished with exit code 0
从结果中可以看到，1,2,3,4都被丢弃了。
DiscardPolicy 该策略默默地丢弃无法处理的任务，不予任何处理。
代码如下：
1 package cn.concurrent.executor;
2
3 import java.util.concurrent.ArrayBlockingQueue;
4 import java.util.concurrent.PriorityBlockingQueue;
5 import java.util.concurrent.ThreadPoolExecutor;
6 import java.util.concurrent.TimeUnit;
7
8 /**
9 * Created by spark on 17-9-24.
10 */
11 public class DiscardPolicy {
12
13 public static void main(String[] args) {
14 ThreadPoolExecutor pool=new ThreadPoolExecutor(1,1,0, TimeUnit.SECONDS,
15 new ArrayBlockingQueue
16 //添加饱和策略为丢弃策略
17 pool.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());
18 for (int i = 0; i < 6; i++) {
19 MyRunnable myRunnable = new MyRunnable("this is " + i + " task");
20 pool.submit(myRunnable);
21 }
22 pool.shutdown();
23 }
24 static class MyRunnable implements Runnable {
25
26 private String name;
27
28 public MyRunnable(String name) {
29 this.name = name;
30 }
31
32 @Override
33 public void run() {
34 System.err.println(this.name + ": is running.");
35 try {
36 Thread.sleep(300);
37 } catch (InterruptedException e) {
38 e.printStackTrace();
39 }
40 }
41 }
42 }
结果如下：
1 /usr/lib/jvm/java-1.8.0-openjdk-amd64/bin/java -javaagent:/usr/local/idea/lib/idea_rt.jar=41981:/usr/local/idea/bin -Dfile.encoding=UTF-8 -classpath /usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/charsets.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/cldrdata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/dnsns.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/icedtea-sound.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/jaccess.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/localedata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/nashorn.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunec.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunpkcs11.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/zipfs.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jce.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jsse.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/management-agent.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/resources.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/rt.jar:/home/spark/IdeaProjects/thread/thread/target/classes:/home/spark/.m2/repository/com/lmax/disruptor/3.3.2/disruptor-3.3.2.jar cn.concurrent.executor.DiscardPolicy
2 this is 0 task: is running.
3 this is 1 task: is running.
4
5 Process finished with exit code 0
从结果可以看出，2,3,4,5任务都被丢弃了。
线程池pool的"最大池大小"和"核心池大小"都为1(THREADS_SIZE)，这意味着"线程池能同时运行的任务数量最大只能是1"。线程池pool的阻塞队列是ArrayBlockingQueue，ArrayBlockingQueue是一个有界的阻塞队列，ArrayBlockingQueue的容量为1。这也意味着线程池的阻塞队列只能有一个线程池阻塞等待。根据""中分析的execute()代码可知：线程池中共运行了2个任务。第1个任务直接放到Worker中，通过线程去执行；第2个任务放到阻塞队列中等待。其他的任务都被丢弃了！
修改线程池中的队列为PriorityBlockingQueue看看结果
1 package cn.concurrent.executor;
2
3 import java.util.concurrent.ArrayBlockingQueue;
4 import java.util.concurrent.PriorityBlockingQueue;
5 import java.util.concurrent.ThreadPoolExecutor;
6 import java.util.concurrent.TimeUnit;
7
8 /**
9 * Created by spark on 17-9-24.
10 * 13 */
14 public class DiscardPolicy2 {
15
16 public static void main(String[] args) {
17 ThreadPoolExecutor pool=new ThreadPoolExecutor(1,1,0, TimeUnit.SECONDS,
18 new PriorityBlockingQueue<>(1));
19 //添加饱和策略为丢弃策略
20 pool.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());
21 for (int i = 0; i < 6; i++) {
22 MyRunnable myRunnable = new MyRunnable("this is " + i + " task");
23 pool.submit(myRunnable);
24 }
25 pool.shutdown();
26 }
27 static class MyRunnable implements Runnable {
28
29 private String name;
30
31 public MyRunnable(String name) {
32 this.name = name;
33 }
34
35 @Override
36 public void run() {
37 System.err.println(this.name + ": is running.");
38 try {
39 Thread.sleep(300);
40 } catch (InterruptedException e) {
41 e.printStackTrace();
42 }
43 }
44 }
45 }
结果如下：
/usr/lib/jvm/java-1.8.0-openjdk-amd64/bin/java -javaagent:/usr/local/idea/lib/idea_rt.jar=42797:/usr/local/idea/bin -Dfile.encoding=UTF-8 -classpath /usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/charsets.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/cldrdata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/dnsns.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/icedtea-sound.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/jaccess.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/localedata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/nashorn.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunec.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunpkcs11.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/zipfs.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jce.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jsse.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/management-agent.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/resources.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/rt.jar:/home/spark/IdeaProjects/thread/thread/target/classes:/home/spark/.m2/repository/com/lmax/disruptor/3.3.2/disruptor-3.3.2.jar cn.concurrent.executor.DiscardPolicy2
Exception in thread "main" java.lang.ClassCastException: java.util.concurrent.FutureTask cannot be cast to java.lang.Comparable
at java.util.concurrent.PriorityBlockingQueue.siftUpComparable(PriorityBlockingQueue.java:357)
at java.util.concurrent.PriorityBlockingQueue.offer(PriorityBlockingQueue.java:489)
at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1371)
at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:112)
at cn.concurrent.executor.DiscardPolicy2.main(DiscardPolicy2.java:23)
this is 0 task: is running.
报错的原因是因为我们的任务没有优先级，因此应该实现Comparaable接口再看看
1 package cn.concurrent.executor;
2
3 import java.util.concurrent.ArrayBlockingQueue;
4 import java.util.concurrent.PriorityBlockingQueue;
5 import java.util.concurrent.ThreadPoolExecutor;
6 import java.util.concurrent.TimeUnit;
7
8 /**
9 * Created by spark on 17-9-24.
10 * 线程池pool的"最大池大小"和"核心池大小"都为1(THREADS_SIZE)，这意味着"线程池能同时运行的任务数量最大只能是1"。
11 * 线程池pool的阻塞队列是ArrayBlockingQueue，ArrayBlockingQueue是一个有界的阻塞队列，ArrayBlockingQueue的容量为1。这也意味着线程池的阻塞队列只能有一个线程池阻塞等待。
12 * 根据""中分析的execute()代码可知：线程池中共运行了2个任务。第1个任务直接放到Worker中，通过线程去执行；第2个任务放到阻塞队列中等待。其他的任务都被丢弃了！
13 */
14 public class DiscardPolicy2 {
15
16 public static void main(String[] args) {
17 ThreadPoolExecutor pool = new ThreadPoolExecutor(1, 1, 0, TimeUnit.SECONDS,
18 new PriorityBlockingQueue<>(1));
19 //添加饱和策略为丢弃策略
20 pool.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());
21 for (int i = 0; i < 6; i++) {
22 MyRunnable myRunnable = new MyRunnable("this is " + i + " task", i);
23 pool.execute(myRunnable);
24 }
25 pool.shutdown();
26 }
27
28 static class MyRunnable implements Runnable, Comparable {
29
30 private String name;
31 private int num;
32
33 public MyRunnable(String name, int num) {
34 this.name = name;
35 this.num = num;
36 }
37
38 public MyRunnable(String name) {
39 this.name = name;
40 }
41
42 @Override
43 public void run() {
44 System.err.println(this.name + ": is running.");
45 try {
46 Thread.sleep(300);
47 } catch (InterruptedException e) {
48 e.printStackTrace();
49 }
50 }
51
52 @Override
53 public int compareTo(Object o) {
54 return 0;
55 }
56 }
57 }
结果：
/usr/lib/jvm/java-1.8.0-openjdk-amd64/bin/java -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:41534,suspend=y,server=n -Dfile.encoding=UTF-8 -classpath /usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/charsets.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/cldrdata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/dnsns.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/icedtea-sound.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/jaccess.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/localedata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/nashorn.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunec.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunpkcs11.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/zipfs.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jce.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jsse.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/management-agent.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/resources.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/rt.jar:/home/spark/IdeaProjects/thread/thread/target/classes:/home/spark/.m2/repository/com/lmax/disruptor/3.3.2/disruptor-3.3.2.jar:/usr/local/idea/lib/idea_rt.jar cn.concurrent.executor.DiscardPolicy2
Connected to the target VM, address: '127.0.0.1:41534', transport: 'socket'
this is 0 task: is running.
this is 1 task: is running.
this is 5 task: is running.
this is 4 task: is running.
this is 3 task: is running.
this is 2 task: is running.
Disconnected from the target VM, address: '127.0.0.1:41534', transport: 'socket'
Process finished with exit code 0
这里使用execute没有使用submit是因为submit返回的结果为FutureTask，这个类没有实现Comparable
CallerRunsPolicy 该策略只要线程池未关闭，该策略直接在调用者线程中，运行当前被丢弃的任务（白话就是不会抛弃线程，也不抛出异常，而是将任务回退到调用者， 从而降低新任务的流量），这样会影响QPS。
代码如下：
1 package cn.concurrent.executor;
2
3 import java.util.concurrent.ArrayBlockingQueue;
4 import java.util.concurrent.ThreadPoolExecutor;
5 import java.util.concurrent.TimeUnit;
6
7 /**
8 * Created by spark on 17-9-24.
9 */
10 public class CallerRunsPolicyDemo {
11 public static void main(String[] args) {
12 ThreadPoolExecutor pool=new ThreadPoolExecutor(1,1,0, TimeUnit.SECONDS,
13 new ArrayBlockingQueue
14 //添加饱和策略为丢弃策略
15 pool.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
16 for (int i = 0; i < 6; i++) {
17 MyRunnable myRunnable = new MyRunnable("this is " + i + " task");
18 pool.submit(myRunnable);
19 }
20 pool.shutdown();
21 }
22 static class MyRunnable implements Runnable {
23
24 private String name;
25
26 public MyRunnable(String name) {
27 this.name = name;
28 }
29
30 @Override
31 public void run() {
32 System.err.println(this.name + ": is running.");
33 try {
34 Thread.sleep(300);
35 } catch (InterruptedException e) {
36 e.printStackTrace();
37 }
38 }
39 }
40 }
结果如下：
/usr/lib/jvm/java-1.8.0-openjdk-amd64/bin/java -javaagent:/usr/local/idea/lib/idea_rt.jar=40487:/usr/local/idea/bin -Dfile.encoding=UTF-8 -classpath /usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/charsets.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/cldrdata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/dnsns.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/icedtea-sound.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/jaccess.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/localedata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/nashorn.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunec.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunpkcs11.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/zipfs.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jce.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jsse.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/management-agent.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/resources.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/rt.jar:/home/spark/IdeaProjects/thread/thread/target/classes:/home/spark/.m2/repository/com/lmax/disruptor/3.3.2/disruptor-3.3.2.jar cn.concurrent.executor.CallerRunsPolicyDemo
this is 2 task: is running.
this is 0 task: is running.
this is 3 task: is running.
this is 1 task: is running.
this is 5 task: is running.
this is 4 task: is running.
Process finished with exit code 0
我们还可以自定义饱和策略：如下：
1 package cn.concurrent;
2
3 import java.util.concurrent.*;
4
5 /**
6 * Created by spark on 17-9-3.
7 * 主要演示线程池的拒绝策略实现的接口RejectedExecutionHandler
8 */
9 public class RejectThreadPoolDemo {
10
11 public static class MyTask implements Runnable {
12 @Override
13 public void run() {
14 System.out.println(System.currentTimeMillis() + ":Thread ID:" + Thread.currentThread().getId());
15 try {
16 Thread.sleep(100);
17 } catch (InterruptedException e) {
18 e.printStackTrace();
19 }
20 }
21 }
22
23 //实现RejectExecutionHandler
24 public static void main(String[] args) throws InterruptedException {
25 MyTask myTask = new MyTask();
26 //创建一个线程池
27 ExecutorService es = new ThreadPoolExecutor(5, 5, 0L, TimeUnit.MILLISECONDS,
28 new LinkedBlockingDeque
29 Executors.defaultThreadFactory(),
30 new RejectedExecutionHandler() {
31 //自定义拒绝策略的处理
32 @Override
33 public void rejectedExecution(Runnable runnable, ThreadPoolExecutor threadPoolExecutor) {
34 System.out.println(runnable.toString() + " is discard");
35 }
36 });
37 for(int i=0;i 38 es.submit(myTask); 39 Thread.sleep(10); 40 } 41 } 42 } 结果如下： /usr/lib/jvm/java-1.8.0-openjdk-amd64/bin/java -javaagent:/usr/local/idea/lib/idea_rt.jar=35478:/usr/local/idea/bin -Dfile.encoding=UTF-8 -classpath /usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/charsets.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/cldrdata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/dnsns.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/icedtea-sound.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/jaccess.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/localedata.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/nashorn.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunec.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/sunpkcs11.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/ext/zipfs.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jce.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/jsse.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/management-agent.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/resources.jar:/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre/lib/rt.jar:/home/spark/IdeaProjects/thread/thread/target/classes:/home/spark/.m2/repository/com/lmax/disruptor/3.3.2/disruptor-3.3.2.jar cn.concurrent.RejectThreadPoolDemo 1506244149620:Thread ID:10 1506244149630:Thread ID:11 1506244149640:Thread ID:12 1506244149651:Thread ID:13 1506244149661:Thread ID:14 1506244149720:Thread ID:10 1506244149730:Thread ID:11 1506244149740:Thread ID:12 1506244149751:Thread ID:13 1506244149761:Thread ID:14 1506244149821:Thread ID:10 1506244149830:Thread ID:11 1506244149841:Thread ID:12 1506244149851:Thread ID:13 1506244149862:Thread ID:14 java.util.concurrent.FutureTask@63947c6b is discard java.util.concurrent.FutureTask@2b193f2d is discard java.util.concurrent.FutureTask@355da254 is discard java.util.concurrent.FutureTask@4dc63996 is discard java.util.concurrent.FutureTask@d716361 is discard 1506244149921:Thread ID:10 1506244149930:Thread ID:11 1506244149941:Thread ID:12 1506244149951:Thread ID:13 1506244149962:Thread ID:14 java.util.concurrent.FutureTask@6ff3c5b5 is discard java.util.concurrent.FutureTask@3764951d is discard java.util.concurrent.FutureTask@4b1210ee is discard java.util.concurrent.FutureTask@4d7e1886 is discard java.util.concurrent.FutureTask@3cd1a2f1 is discard 1506244150023:Thread ID:10 1506244150031:Thread ID:11 可以看到，饱和策略生效了，在实际应用中，我们可以记录日志，分析系统的负载和任务丢失的情况。 记录点点滴滴，有很多要学习，望大家指点。