Java8 CompletableFuture非同步任務

無返回值呼叫

import java.util.concurrent.CompletableFuture;
 
public class TestDemo {
 
    public static void main(String[] args) {
        System.out.println("進入主執行緒=============");
        CompletableFuture.runAsync(()->getNum());
        System.out.println("主執行緒結束=============");
    }
	
	public void getNum(){
		System.out.println("執行執行緒=============");
	}
}

有返回值呼叫

import java.util.concurrent.CompletableFuture;
 
public class TestDemo {
 
    public static void main(String[] args) throws ExecutionException, InterruptedException {
		// 無返回值 runAsync() 有返回值 supplyAsync()
        CompletableFuture<Integer> future = CompletableFuture.supplyAsync(() -> getNum());
        System.out.println(future.get());
    }

    private static Integer getNum() {
        return 5 / 2;
    }
}

使用自定義執行緒池

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
 
public class TestDemo {
    /**
     * 自定義執行緒池
     */
    public static ExecutorService service = Executors.newFixedThreadPool(5);

    public static void main(String[] args) throws ExecutionException, InterruptedException {
		// 無返回值 runAsync() 有返回值 supplyAsync()
        CompletableFuture<Integer> future = CompletableFuture.supplyAsync(() -> getNum(),service);
        System.out.println(future.get());
    }

    private static Integer getNum() {
        return 5 / 2;
    }
}

處理異常

handleAsync
該方法有兩個引數，一種一個是上一步的結果，另一個則是上一步的異常。而且如果出現異常則第一個引數為null，如果沒有異常則第二個引數為null。

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
 
public class TestDemo {
    /**
     * 自定義執行緒池
     */
    public static ExecutorService service = Executors.newFixedThreadPool(5);

    public static void main(String[] args) throws ExecutionException, InterruptedException {
		// 無返回值 runAsync() 有返回值 supplyAsync()
        CompletableFuture<Integer> future = CompletableFuture.supplyAsync(() -> getNum(),service).handleAsync((res, e) -> {
            if (res != null) {
                return res;
            }
            if (e != null) {
                return 0;
            }
            return 0;
        });
        System.out.println(future.get());
    }

    private static Integer getNum() {
	    // by zero 
        return 5 / 0;
    }
}

還有其他很多方法，用到的時候可以去了解。