1背景
在回顾线程池的使用时，发现submit和execute，有很多相似之处，并对其进行了进一步的探索。
先上结论：
线程池中，不需要返回值的pool.execute(runnable)
线程池中，需要返回值的pool.submit(callable)，或者，先进行包装FutureTask futureTask = new FutureTask(callable);再executor.submit(futureTask);
普通线程中，不需要返回值可以直接使用new Thread(runnable).start()
普通线程中，需要返回值，先进行包装FutureTask futureTask = new FutureTask(callable);再new Thread(futureTask).start()，结果通过futureTask的属性方法进行查看
（有可能还有其他方法，水平有限，可能暂未列出）
2代码实践
最原始的submit和execute代码实践，submit执行callable接口类，execute执行runnable接口类
package com.zte.线程池实践;
import java.util.concurrent.*;
public class CallableTask implements Callable, Runnable {
private int flag;
public static int ExceptionNumber = 666;
public CallableTask(int flag) {
this.flag = flag;
}
@Override
public String call() throws Exception {
System.out.println(Thread.currentThread().getName());
if (flag == ExceptionNumber) {
throw new Exception("flag is ExceptionNumber");
}
return flag % 2 == 0 ? "偶数" : "奇数";
}
@Override
public void run() {
System.out.println(Thread.currentThread().getName());
System.out.println(flag % 2 == 0 ? "偶数" : "奇数");
}
public static void main(String[] args) throws InterruptedException, ExecutionException {
ExecutorService cachedThreadPool = Executors.newCachedThreadPool();
Runnable runnable1 = new CallableTask(1);
Runnable runnable2 = new CallableTask(2);
Runnable runnable3 = new CallableTask(666);
cachedThreadPool.execute(runnable1);
cachedThreadPool.execute(runnable2);
cachedThreadPool.execute(runnable3);
Thread.sleep(1000);
Callable callable1 = new CallableTask(1);
Callable callable2 = new CallableTask(2);
Callable callable3 = new CallableTask(666);
Future future1 = cachedThreadPool.submit(callable1);
Future future2 = cachedThreadPool.submit(callable2);
Future future3 = cachedThreadPool.submit(callable3);
while (true) {
if (future1.isDone() && future2.isDone() && future3.isDone()) {
System.out.println("=====================inside=================while=====================");
System.out.println(future1.get());//future 的 get 方法本身就是阻塞的，直接调用时会一直等到有了结果才会执行下一条语句
System.out.println(future2.get());
try {
//get 只能get到call方法的返回值，抛出的异常从调用get方法时一同抛出，异常还是应该使用try catch 捕捉
System.out.println(future3.get());
} catch (Exception e) {
System.out.println(e);
}
// System.out.println(future3.get());
break;
}
System.out.println("last line in while cycle");
}
cachedThreadPool.shutdown();
}
}
3 源码解析
可参考这篇大佬的文章：
https://blog.csdn.net/kai3123919064/article/details/90343380
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