import java.util.concurrent.TimeUnit;
public class ThreadPoolTask implements Runnable {
private final Object threadPoolTaskData;
private static long consumerTaskSleepTime = 2L;
public ThreadPoolTask(Object tasks) {
this.threadPoolTaskData = tasks;
}
@Override
public void run() {
System.out.println("start :" + threadPoolTaskData);
try {
TimeUnit.SECONDS.sleep(consumerTaskSleepTime);
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("finish " + threadPoolTaskData);
}
}
Abort(中止)策略：该策略会抛出未检查的RejectedExecutionException。调用者可以捕获这个异常，然后根据需求编写自己的处理代码。代码如下：
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class ThreadPool {
private static int executePrograms = 0;
private static int produceTaskMaxNumber = 10;
/**
* @param args
*/
public static void main(String[] args) {
ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 4, 3,
TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(3),new ThreadPoolExecutor.AbortPolicy());
for(int i = 0 ; i < produceTaskMaxNumber; i ++) {
try {
String task = "task@ " + i;
System.out.println("put " + task);
threadPoolExecutor.execute(new ThreadPoolTask(task));
TimeUnit.SECONDS.sleep(executePrograms);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
程序的执行结果如下：
put task@ 0 put task@ 1 start :task@ 0 put task@ 2 put task@ 3 put task@ 4 put task@ 5 start :task@ 1 put task@ 6 start :task@ 5 put task@ 7 start :task@ 6 put task@ 8 java.util.concurrent.RejectedExecutionException put task@ 9 at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:1774) at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:768) at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:656) at com.bohai.thread.pool.ThreadPool.main(ThreadPool.java:22) java.util.concurrent.RejectedExecutionException at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:1774) at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:768) at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:656) at com.bohai.thread.pool.ThreadPool.main(ThreadPool.java:22) java.util.concurrent.RejectedExecutionException at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:1774) at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:768) at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:656) at com.bohai.thread.pool.ThreadPool.main(ThreadPool.java:22) finish task@ 0 start :task@ 2 finish task@ 1 start :task@ 3 finish task@ 5 start :task@ 4 finish task@ 6 finish task@ 2 finish task@ 3 finish task@ 4
分析运行结果：
corepoolsize = 2 ,maxpoolsize = 4,queue size = 3。运行中的线程数+队列中等待的线程数 = 7，及提交的线程数大于7时，会抛出异常。
DiscardPolicy 策略会悄悄抛弃新提交的任务：代码如下：
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class ThreadPool {
private static int executePrograms = 0;
private static int produceTaskMaxNumber = 10;
/**
* @param args
*/
public static void main(String[] args) {
ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 4, 3,
TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(3),new ThreadPoolExecutor.DiscardPolicy());
for(int i = 0 ; i < produceTaskMaxNumber; i ++) {
try {
String task = "task@ " + i;
System.out.println("put " + task);
threadPoolExecutor.execute(new ThreadPoolTask(task));
TimeUnit.SECONDS.sleep(executePrograms);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
执行结果如下：
put task@ 0 put task@ 1 start :task@ 0 put task@ 2 put task@ 3 put task@ 4 put task@ 5 start :task@ 1 put task@ 6 put task@ 7 put task@ 8 put task@ 9 start :task@ 6 start :task@ 5 finish task@ 0 finish task@ 6 start :task@ 2 finish task@ 1 start :task@ 3 start :task@ 4 finish task@ 5 finish task@ 2 finish task@ 3 finish task@ 4
分析结果：
提交的任务数有10个，开始和结束的任务数7个。抛弃了新提交的任务7、8、9。
DiscardOldestPolicy 抛弃旧的线程。代码如下：
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class ThreadPool {
private static int executePrograms = 0;
private static int produceTaskMaxNumber = 10;
/**
* @param args
*/
public static void main(String[] args) {
ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 4, 3,
TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(3),new ThreadPoolExecutor.DiscardOldestPolicy());
for(int i = 0 ; i < produceTaskMaxNumber; i ++) {
try {
String task = "task@ " + i;
System.out.println("put " + task);
threadPoolExecutor.execute(new ThreadPoolTask(task));
TimeUnit.SECONDS.sleep(executePrograms);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
执行结果如下：
put task@ 0 put task@ 1 put task@ 2 put task@ 3 put task@ 4 put task@ 5 put task@ 6 put task@ 7 put task@ 8 put task@ 9 start :task@ 0 start :task@ 5 start :task@ 1 start :task@ 6 finish task@ 0 start :task@ 7 finish task@ 5 start :task@ 8 finish task@ 1 start :task@ 9 finish task@ 6 finish task@ 7 finish task@ 8 finish task@ 9
对结果进行分析：
线程池抛弃了2、3、4，线程0、1没有进入队列，进行开始执行。所以不会被抛出。
CallerRunsPolicy 策略实现一种调节机制，该策略既不会抛弃任务，也不会抛出异常，而是将某些任务回退到调用者，从而降低新任务的流量。它不会在线程池的某个线程中执行新提交的任务，而是在一个调用了execute的线程中执行该任务。代码如下：
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class ThreadPool {
private static int executePrograms = 0;
private static int produceTaskMaxNumber = 10;
/**
* @param args
*/
public static void main(String[] args) {
ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 4, 3,
TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(3),new ThreadPoolExecutor.CallerRunsPolicy());
for(int i = 0 ; i < produceTaskMaxNumber; i ++) {
try {
String task = "task@ " + i;
System.out.println("put " + task);
threadPoolExecutor.execute(new ThreadPoolTask(task));
TimeUnit.SECONDS.sleep(executePrograms);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
运行结果如下：
put task@ 0 put task@ 1 put task@ 2 put task@ 3 put task@ 4 put task@ 5 start :task@ 1 put task@ 6 put task@ 7 start :task@ 7 start :task@ 6 start :task@ 0 start :task@ 5 finish task@ 7 put task@ 8 finish task@ 1 start :task@ 2 finish task@ 6 finish task@ 0 finish task@ 5 put task@ 9 start :task@ 3 start :task@ 8 start :task@ 4 finish task@ 2 start :task@ 9 finish task@ 3 finish task@ 8 finish task@ 4 finish task@ 9
对结果进行分析：
所有的线程都执行了。
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