CompletableFuture源码详解之java.util.concurrent.CompletableFuture#supplyAsync(java.util.function.Supplier<U>)

/**
     * Returns a new CompletableFuture that is asynchronously completed
     * by a task running in the {@link ForkJoinPool#commonPool()} with
     * the value obtained by calling the given Supplier.
     *
     * @param supplier a function returning the value to be used
     * to complete the returned CompletableFuture
     * @param <U> the function's return type
     * @return the new CompletableFuture
     */
    public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier) {
        return asyncSupplyStage(asyncPool, supplier);
    }

　　CompletableFuture下的supplyAsync方法是一个执行异步任务且有返回结果的任务，使用例子如下：

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;

/**
 * 测试类
 * @author yangchangkui
 */
public class TestMy {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        long start = System.currentTimeMillis();
        CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return "hello";
        });
        //判断是否已经完成
        System.out.println("耗时："+(System.currentTimeMillis()-start)+"，isDone:"+completableFuture.isDone());
        //阻塞获取结果
        String result = completableFuture.get();
        System.out.println("耗时："+(System.currentTimeMillis()-start)+"，result:"+result);
        //判断是否已经完成
        System.out.println("耗时："+(System.currentTimeMillis()-start)+"，isDone:"+completableFuture.isDone());

    }
}

　　执行结果如下，显然，达到了异步执行的效果，比如在一些调用很多外部接口的聚合接口，只要接口不作为入参，那就可以进行异步执行，最后阻塞拿结果，提高接口的QPS，提高系统性能。