ThreadPoolExecutor的说明
ThreadPoolExecutor常见的操作主要有以下几个方法：
getPoolSize()：返回线程池实际的线程数。getActiveCount()：返回在执行者中正在执行任务的线程数。getCompletedTaskCount()：返回执行者完成的任务数。submit(): 提交一个线程给线程执行者，如果执行者有空余线程，则直接执行；否则等待直到有空闲线程。这里调用sumbit后，并不会阻塞调用线程。调用者所在的线程和执行的线程并发运行。
下面要着重介绍两个方法：
shutdown(): 调用这个方法后，线程执行者在完成当前已经提交的所有任务后，结束运行。
a. 在主线程中如果调用线程执行者的这个方法，并不会使线程执行者中已经submit的任务中断（无论是待执行、执行中）
b. 调用shutdown会通知执行者，后面提交的任务“不允许接受”，在shutdown后提交任务，会抛出RejectedExecutionException的异常信息。shutdownNow(): 调用这个方法后，立即停止执行者的运行。返回待执行的Task。
a. 中断所有正在执行的线程: 正在执行的线程会收到中断信息。抛出InterruptedException
b. 后面提交的任务“不允许接受”，在shutdownNow后再调用submit提交任务，会抛出RejectedExecutionException的异常信息。
code1：
public class ThreadPoolTest {
public static void main(String[] args) {
ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newCachedThreadPool();
for (int i = 0; i < 3; i++) {
executor.submit(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(100);
System.out.println("sub thread classs");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
}
executor.shutdown();
System.out.println("Main classs");
}
}
结果：
Main classs sub thread classs sub thread classs sub thread classs
说明：
调用executor.submit后，并不会阻塞主线程。主线程和提交到执行者中的线程并发执行。
code2：
public class ThreadPoolTest {
public static void main(String[] args) {
ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newCachedThreadPool();
for (int i = 0; i < 3; i++) {
executor.submit(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(100);
System.out.println("sub thread classs");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
}
executor.shutdown();
executor.submit(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(100);
System.out.println("sub thread classs");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
System.out.println("Main classs");
}
}
结果：
Exception in thread "main" java.util.concurrent.RejectedExecutionException: Task [email protected] rejected from java.util.concurrent. [email protected][Shutting down, pool size = 3, active threads = 3, queued tasks = 0, completed tasks = 0] at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2048) at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:821) at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1372) at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:110) at ThreadPoolTest.ThreadPoolTest.main(ThreadPoolTest.java:29) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134) sub thread classs sub thread classs sub thread classs
说明：
调用executor.shutdown()后，如果再调用submit()方法，调用线程会抛出rejectedExecution，如果没有try，cacth直接中断
后续的操作。
code3：
public class ThreadPoolTest {
public static void main(String[] args) {
ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newCachedThreadPool();
for (int i = 0; i < 3; i++) {
executor.submit(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(100);
System.out.println("sub thread classs");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
}
List<Runnable> list=executor.shutdownNow();
System.out.println("list size:"+list.size());
executor.submit(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(100);
System.out.println("sub thread classs");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
System.out.println("Main classs");
}
}
结果：
list size:0 java.lang.InterruptedException: sleep interrupted at java.lang.Thread.sleep(Native Method) at ThreadPoolTest.ThreadPoolTest$1.run(ThreadPoolTest.java:16) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) at java.util.concurrent.FutureTask.run(FutureTask.java:166) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:722) java.lang.InterruptedException: sleep interrupted at java.lang.Thread.sleep(Native Method) at ThreadPoolTest.ThreadPoolTest$1.run(ThreadPoolTest.java:16) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) at java.util.concurrent.FutureTask.run(FutureTask.java:166) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:722) java.lang.InterruptedException: sleep interrupted at java.lang.Thread.sleep(Native Method) at ThreadPoolTest.ThreadPoolTest$1.run(ThreadPoolTest.java:16) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) at java.util.concurrent.FutureTask.run(FutureTask.java:166) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:722) Exception in thread "main" java.util.concurrent.RejectedExecutionException: Task [email protected] rejected from [email protected] [Shutting down, pool size = 2, active threads = 2, queued tasks = 0, completed tasks = 1] at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2048) at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:821) at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1372) at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:110) at ThreadPoolTest.ThreadPoolTest.main(ThreadPoolTest.java:25) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
说明：
调用shutDownNow()后，直接中断所有的线程。并且后面submit()task会抛出rejectedExecution。
时间： 2024-08-30 11:34:27