java - 错误: cannot find symbol for correctly used methods (I think)

我有

ExecutorService tpool = new ThreadPoolExecutor(5, 50, 5, TimeUnit.MILLISECONDS, new SynchronousQueue<>());

后来

int y = tpool.getPoolSize();

但是当我尝试编译时说错误:找不到符号
我已经尝试过这些导入(我最初使用.concurrent。*，然后又扔了后两个):

import java.util.concurrent.*;
import java.util.concurrent.AbstractExecutorService;
import java.util.concurrent.ThreadPoolExecutor;

出于好奇，我也尝试过

boolean x = tpool.isShutdown();
String z = tpool.toString();
long a = tpool.getTaskCount();
int b = tpool.getCorePoolSize();

仅.isShutdown和.getCorepoolSize不会给出编译器错误。
我在这里做错什么了吗？

最佳答案

如果您想要这些功能，似乎您正在寻找:

import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

...

ThreadPoolExecutor tpool = ..

并不是 :

ExecutorService tpool = ...