CompletableFuture源码详解之java.util.concurrent.CompletableFuture#supplyAsync(java.util.function.Supplier...-优快云博客

本文详细探讨了Java中的CompletableFuture#supplyAsync方法，该方法用于执行异步任务并获取返回结果。通过示例展示了如何利用此特性实现异步执行，提升接口QPS与系统性能。

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/**
     * 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());

    }
}