异步一般用来处理耗时非常多的计算，如果你的计算量不是很大，调用异步方法反而没有执行来的快，我在这里为大家简单的整理一下异步的知识以及用法，我写了一个Main的类，大家可以跑其中的一个方法，把其他的注释掉，这样就可以对异步有一个大致的了解了。
| 方法 | 入参 | 返回值 |
|---|---|---|
| runAsync | Runnable | Void |
| thenAccept | T | void |
| thenApply | T | U |
| thenRun | Runnable | Void |
| supplyAsync | T | U |
/**
* main
*
* @author 719383495@qq.com |719383495qq@gmail.com |gfu
* @date 2019/8/30
*/
public class Main {
public static void main(String[] args) throws InterruptedException {
Async async = new Async();
async.doAsync0();
async.doAsync1();
async.doAsync2();
async.doAsync3();
async.doAsync4();
Thread.sleep(6000);
}
}
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
/**
* async
*
* @author 719383495@qq.com |719383495qq@gmail.com |gfu
* @date 2019/8/30
*/
public class Async {
static final int NINE_MULTI_BY_NINE_LENGTH = 10;
public long print() {
System.out.println(Thread.currentThread().getName() + Thread.currentThread().getId() + ":");
long start0 = System.nanoTime();
System.out.println("----------start---------");
for (int i = 0; i < NINE_MULTI_BY_NINE_LENGTH; i++) {
for (int j = 0; j < NINE_MULTI_BY_NINE_LENGTH; j++) {
System.out.print(i * j + " ");
}
System.out.println();
}
long end0 = System.nanoTime();
System.out.println(Thread.currentThread().getName() + Thread.currentThread().getId() + ":" + (end0 - start0));
return end0 - start0;
}
public void doAsync0() {
CompletableFuture.runAsync(this::print);
}
/**
* need return value
*/
public void doAsync1() {
CompletableFuture.supplyAsync(() -> print());
}
/**
* you can see it's method to judge whether must need params or return
* thenAccept can accept pre-stage's result as params
* thenAccept and thenApply must need params
* thenAccept can return void but thenApply need to have a return value
*/
public void doAsync2() {
CompletableFuture.supplyAsync(() -> print())
.thenAccept((i) -> {
System.out.println("-----------------------------------------------");
System.out.println(Thread.currentThread().getName() + Thread.currentThread().getId() + "#" + i);
});
}
/**
* complete and CompletableFuture's get method can let you get it.s async calculate result
*/
public void doAsync3() {
CompletableFuture cf = new CompletableFuture();
cf.complete("hello");
try {
System.out.println(cf.get());
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
public void doAsync4() {
CompletableFuture cf0 = CompletableFuture.supplyAsync(() -> print());
CompletableFuture cf1 = CompletableFuture.supplyAsync(() -> "world");
CompletableFuture cf2 = CompletableFuture.supplyAsync(() -> "java8");
CompletableFuture cf = CompletableFuture.allOf(cf0);
try {
System.out.println(Thread.currentThread().getName() + Thread.currentThread().getId() + ":" + cf0.get());
System.out.println(Thread.currentThread().getName() + Thread.currentThread().getId() + ":" + cf1.get());
System.out.println(Thread.currentThread().getName() + Thread.currentThread().getId() + ":" + cf2.get());
System.out.println(cf.get());
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
}
