这是
example的一些示例代码.我需要知道的是在calllable上调用call()的时候？触发它的是什么？
public class CallableExample {
public static class WordLengthCallable
implements Callable {
private String word;
public WordLengthCallable(String word) {
this.word = word;
}
public Integer call() {
return Integer.valueOf(word.length());
}
}
public static void main(String args[]) throws Exception {
ExecutorService pool = Executors.newFixedThreadPool(3);
Set<Future<Integer>> set = new HashSet<Future<Integer>>();
for (String word: args) {
Callable<Integer> callable = new WordLengthCallable(word);
Future<Integer> future = pool.submit(callable); //**DOES THIS CALL call()?**
set.add(future);
}
int sum = 0;
for (Future<Integer> future : set) {
sum += future.get();//**OR DOES THIS CALL call()?**
}
System.out.printf("The sum of lengths is %s%n",sum);
System.exit(sum);
}
}
解决方法
一旦提交了callable,执行程序就会调度callable以便执行.根据执行程序的不同,这可能会直接发生,也可能在线程可用后发生.
另一方面,调用get只等待检索计算结果.
所以准确地说：在中间提交被调用和调用返回之间,调用可调用.