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从工作中返回值
import java.util.ArrayList;
import java.util.concurrent.*;
class TaskWithResult implements Callable<String> { // 要想得到返回值能够实现 Callable 接口, 类型参数是返回值的类型
private int id;
public TaskWithResult(int id) {this.id = id;}
@Override
public String call() throws Exception { // 实现 call() 办法,而不是 run()
return "result of TaskWithResult" + id;
}
}
public class CallableDemo {public static void main(String[] args) {ExecutorService exec = Executors.newCachedThreadPool();
ArrayList<Future<String>> results = new ArrayList<>(); //submit 办法会产生 Future 对象
for (int i = 0; i < 10; i++) {results.add(exec.submit(new TaskWithResult(i)));// 必须应用 ExectorService.submit() 办法调用}
for (Future<String> fs :
results) {
try {System.out.println(fs.get()); //get() 办法获取返回的后果,} catch (InterruptedException e) {System.out.println(e);
return;
} catch (ExecutionException e) {System.out.println(e);
}finally {exec.shutdown(); // 敞开
}
}
}
}
- 能够应用 Futrue 对象的 isDone() 办法来查问 Futrue 是否已实现
- 也能够间接调用 get(),get() 办法会等到后果就绪后调用
优先级
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class SimplePriorities implements Runnable{
private int countDown = 5;
private volatile double d;
private int priority;
public SimplePriorities(int priority) {this.priority = priority;}
public String toString(){return Thread.currentThread()+"优先级:"+priority + "计数" + ":"+countDown;
}
@Override
public void run() {Thread.currentThread().setPriority(priority);
while (true) {for (int i = 0; i < 100000; i++) {d += (Math.PI + Math.E) / (double) i;
if (i%1000==0) Thread.yield();}
System.out.println(this);
if (--countDown==0) return;
}
}
public static void main(String[] args) {ExecutorService exec = Executors.newCachedThreadPool();
for (int i = 0; i < 5; i++) {exec.execute(new SimplePriorities(Thread.MIN_PRIORITY));
}
exec.execute(new SimplePriorities(Thread.MAX_PRIORITY));
exec.shutdown();}
}
正文完