我想在Runnable上设置参数,然后获取值。
我写了这段代码。当我运行此代码时,请返回 [2,3,3] 。因为线程共享temp_value。
然后我添加了 sleep ,该 sleep 已过时。结果为 [1、2、3] 。效果很好!但是..这不是真正的多线程,对吗?
即使它正在运行多线程,但我需要等待每个进程完成以获取共享值。
如何解决这个问题?
import java.util.ArrayList;
public class Foo implements Runnable {
private int temp_value;
private ArrayList<Integer> values = new ArrayList<Integer>();
private ArrayList<Integer> newValues = new ArrayList<Integer>();
public Foo(ArrayList<Integer> values) {
this.values = values;
}
public static void main(String[] args) {
// make initial values
ArrayList<Integer> values = new ArrayList<Integer>();
values.add(1);
values.add(2);
values.add(3);
// set values then process and get new values
Foo foo = new Foo(values);
foo.startAppendValue(foo);
System.out.println(foo.getNewValues());
}
public void startAppendValue(Foo foo) {
Thread thread = null;
int max = values.size();
for (int i = 0; i < max; i++) {
foo.temp_value =foo.values.get(i);
thread = new Thread(foo);
thread.start();
// try {
// Thread.sleep(10);
// } catch (Exception e) {
// // TODO: handle exception
// }
}
try {
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
@Override
public void run() {
newValues.add(temp_value);
}
public ArrayList<Integer> getNewValues() {
return this.newValues;
}
}
最佳答案
您可以使用Callable
和ExecutorService
来完成这些工作
public class MyCallable implements Callable<Integer> { //Callable is like Runnable but can return value
private Integer value;
public MyCallable(Integer v) {
value = v;
}
public Integer call() {
return value;
}
public static void main(String[] args) {
ExecutorService exec = Executors.newFixedThreadPool(3); //Creating thread pool with 3 worker threads
List<Integer> values = Arrays.asList(1, 2, 3);
List<Future<Integer>> futures = new ArrayList<>(values.size());
List<Integer> newValues = new ArrayList<>(values.size());
for (Integer v : values) {
futures.add(exec.submit(new MyCallable(v))); //Submit tasks to worker threads to do stuff in background
}
for (Future<Integer> f : futures) {
try {
newValues.add(f.get()); // get calculated result from worker thread or block waiting for result to become available
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
}
System.out.println(newValues);
exec.shutdownNow();
}
}
关于java - 如何在Runnable上设置参数然后获取值?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/52469093/