Java核心复习——CompletableFuture
介绍
JDK1.8引入CompletableFuture类。
使用方法
public class CompletableFutureTest {
private static ExecutorService threadPool = new ThreadPoolExecutor(40, 100,
0L, TimeUnit.MILLISECONDS,
new ArrayBlockingQueue<>(20));
public String B() {
System.out.println("执行方法B");
sleep(5);
return "Function B";
}
public String C() {
System.out.println("执行方法C");
sleep(20);
return "Function C";
}
public void sleep(int i) {
try {
Thread.sleep(i * 1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public void testCompableFuture() {
CompletableFuture<String> future;
try {
//Returns a new CompletableFuture
// that is asynchronously completed by a task running in the given executor
// with the value obtained by calling the given Supplier.
future = CompletableFuture.supplyAsync(() -> B(), threadPool);
//若去掉线程池,有何区别future = CompletableFuture.supplyAsync(() -> B());
sleep(9);
System.out.println(future.toString());
System.out.println(future.isDone());
} catch (RejectedExecutionException e) {
System.out.println("调用搜索列表服务线程满负荷, param:{}");
}
}
public static void main(String[] args) {
CompletableFutureTest test = new CompletableFutureTest();
test.testCompableFuture();
}
}
API
supplyAsync方法
JDK方法描述
/**
* Returns a new CompletableFuture that is asynchronously completed
* by a task running in the given executor 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 executor the executor to use for asynchronous execution
* @param <U> the function's return type
* @return the new CompletableFuture
*/
public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier,
Executor executor) {
return asyncSupplyStage(screenExecutor(executor), supplier);
}
应用场景
请求A的执行方法X,需满足下列需求:
①请求B、C、D中任一一个请求有返回结果,则X方法返回响应结果。
②请求B、C、D中都执行完,则X方法返回响应结果。
源码阅读
依赖关系
参考文档
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