Java中的内部FutureTask
Java中的内部FutureTask
提问于 2012-12-12 21:40:42
我尝试实现一个内部方法，以便在新线程中执行以下代码
MyPojo result = null;
final MyPojo result2 = result;
FutureTask<MyPojo> runnableTask = new FutureTask<MyPojo>(
new Runnable() {
BindJSON<MyPojo> binding;
// Make the URL at which the product list is found
String sourceURLString =
"http://www.....ca/files/{CAT_ID}.json";
@Override
public void run() {
sourceURLString = sourceURLString.replace("{CAT_ID}", catId);
binding = new BindJSON<MyPojo>();
result2 = binding.downloadData(sourceURLString, MyPojo.class);
}
},
result2);
runnableTask.run();所以，现在我得到一个错误:最后一个局部变量result2不能赋值，因为它是在封闭类型中定义的。我看了一下这个答案：Cannot refer to a non-final variable i inside an inner class defined in a different method，但它对我不起作用。我应该怎么做才能让它工作呢？
回答 2
Stack Overflow用户
回答已采纳
发布于 2012-12-12 21:53:09
您可能希望使用Callable，而不是Runnable
// the variable holding the result of a computation
String result = null;
FutureTask<String> runnableTask = new FutureTask<String>(
new Callable<String>() {
public String call() throws Exception {
// (asynchronous) computation ...
return "42";
}
});
System.out.println("result=" + result); // result=null
// this will invoke call, but it will all happen in the *same thread*
runnableTask.run();
// to have a parallel thread execute in the 'background'
// you can use java.util.concurrent.Executors
// Note: an ExecutorService should be .shutdown() properly
// Executors.newSingleThreadExecutor().submit(runnableTask);
// waits for the result to be available
result = runnableTask.get();
// you can also add timeouts:
// result = runnableTask.get(100, TimeUnit.MILLISECONDS);
System.out.println("result=" + result); // result=42http://docs.oracle.com/javase/1.5.0/docs/api/java/util/concurrent/Executors.html：
- Executors
Stack Overflow用户
发布于 2012-12-12 21:52:51
您对FutureTask的使用不是很有用，因为您在同一个线程中执行它。您可以使用executor并提交一个callable来实现您想要的功能：
ExecutorService executor = Executors.newFixedThreadPool(1);
Callable<MyPojo> task = new Callable<MyPojo> () {
BindJSON<MyPojo> binding;
// Make the URL at which the product list is found
String sourceURLString = "http://www.....ca/files/{CAT_ID}.json";
@Override
public MyPojo call() {
sourceURLString = sourceURLString.replace("{CAT_ID}", catId);
binding = new BindJSON<MyPojo>();
return binding.downloadData(sourceURLString, MyPojo.class);
}
};
Future<MyPojo> future = executor.submit(task);
MyPojo result = future.get();注意:对future.get();的调用将被阻塞，直到任务完成。
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原文链接：
https://stackoverflow.com/questions/13841096
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