执行:将其用于火灾并忘记呼叫
submitFuture
:使用它来检查方法调用的结果,并对调用返回的对象采取适当的措施
来自javadocs
submit(Callable<T> task)
提交一个返回值的任务以供执行,并返回一个表示该任务待处理结果的 Future。
Future<?> submit(Runnable task)
提交 Runnable 任务以执行并返回代表该任务的 Future。
void execute(Runnable command)
在将来的某个时间执行给定的命令。该命令可以在新线程、池线程或调用线程中执行,由 Executor 实现决定。
您在使用时必须采取预防措施submit()
。除非您将任务代码嵌入try{} catch{}
块中,否则它会在框架本身中隐藏异常。
示例代码:此代码将Arithmetic exception : / by zero
.
import java.util.concurrent.*;
import java.util.*;
public class ExecuteSubmitDemo{
public ExecuteSubmitDemo()
{
System.out.println("creating service");
ExecutorService service = Executors.newFixedThreadPool(10);
//ExtendedExecutor service = new ExtendedExecutor();
service.submit(new Runnable(){
public void run(){
int a=4, b = 0;
System.out.println("a and b="+a+":"+b);
System.out.println("a/b:"+(a/b));
System.out.println("Thread Name in Runnable after divide by zero:"+Thread.currentThread().getName());
}
});
service.shutdown();
}
public static void main(String args[]){
ExecuteSubmitDemo demo = new ExecuteSubmitDemo();
}
}
输出:
java ExecuteSubmitDemo
creating service
a and b=4:0
通过替换submit()
为execute
() 抛出相同的代码:
代替
service.submit(new Runnable(){
和
service.execute(new Runnable(){
输出:
java ExecuteSubmitDemo
creating service
a and b=4:0
Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero
at ExecuteSubmitDemo$1.run(ExecuteSubmitDemo.java:14)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)
使用 submit() 时如何处理这些类型的场景?
- 使用 try{} catch{} 块代码嵌入您的任务代码(Runnable 或 Callable 实现)
- 实施
CustomThreadPoolExecutor
新解决方案:
import java.util.concurrent.*;
import java.util.*;
public class ExecuteSubmitDemo{
public ExecuteSubmitDemo()
{
System.out.println("creating service");
//ExecutorService service = Executors.newFixedThreadPool(10);
ExtendedExecutor service = new ExtendedExecutor();
service.submit(new Runnable(){
public void run(){
int a=4, b = 0;
System.out.println("a and b="+a+":"+b);
System.out.println("a/b:"+(a/b));
System.out.println("Thread Name in Runnable after divide by zero:"+Thread.currentThread().getName());
}
});
service.shutdown();
}
public static void main(String args[]){
ExecuteSubmitDemo demo = new ExecuteSubmitDemo();
}
}
class ExtendedExecutor extends ThreadPoolExecutor {
public ExtendedExecutor() {
super(1,1,60,TimeUnit.SECONDS,new ArrayBlockingQueue<Runnable>(100));
}
// ...
protected void afterExecute(Runnable r, Throwable t) {
super.afterExecute(r, t);
if (t == null && r instanceof Future<?>) {
try {
Object result = ((Future<?>) r).get();
} catch (CancellationException ce) {
t = ce;
} catch (ExecutionException ee) {
t = ee.getCause();
} catch (InterruptedException ie) {
Thread.currentThread().interrupt(); // ignore/reset
}
}
if (t != null)
System.out.println(t);
}
}
输出:
java ExecuteSubmitDemo
creating service
a and b=4:0
java.lang.ArithmeticException: / by zero