1.Future<V>接口
Runnable接口執行任務是不返回任何值的，Runnable的run()方法的執行結果是void,而Future接口的call方法是有返回結果的，這是Runnable跟Future的區別之壹，它們的另壹個不同之處就是實現了Runnable接口的任務執行是調用ExecutorService的execute(Runnable task)方法，而實現了Future接口的任務是調用ExecutorService的submit(Future task)方法。調用Future的get()方法就能直接得到任務的返回值，該方法會壹直阻塞直到任務的結果出來為止，我們可以調用Future的isDone()方法來判斷該任務的結果是否準備就緒。
[java] view plain copy
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
public class TestFuture {
public static void main(String[] args) throws InterruptedException, ExecutionException {
ExecutorService executor = Executors.newCachedThreadPool();
Future result1 = executor.submit(new Callable() {
@Override
public Integer call() throws Exception {
int sum = 0;
for (int i = 0; i < 10; i++) {
sum += i;
}
return sum;
}
});
Future result2 = executor.submit(new Callable() {
@Override
public Integer call() throws Exception {
int sum = 0;
for (int i = 10; i < 100; i++) {
sum += i;
}
return sum;
}
});
executor.shutdown();
System.out.println(result1.get() + result2.get());
}
}
2.FutureTask類
FutureTask實現了Future接口，將壹個Callable實例作為參數傳給它，就能創建壹個FutureTask實例，然後用ExecutorService的submit方法來執行這個實例。最後同樣是用get方法獲取線程執行後的結果。
[plain] view plain copy
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;
public class TestFutureTask {
public static void main(String[] args) throws InterruptedException, ExecutionException {
ExecutorService executor = Executors.newCachedThreadPool();
Callable task = new Callable() {
@Override
public String call() throws Exception {
return "結果";
}
};
FutureTask ft = new FutureTask(task);
executor.submit(ft);
System.out.println(ft.get());
executor.shutdown();
}
}empty