假如tcp开启了一个120端口监听，那么udp也开启了120端口监听，这样属于抢占吗

java.lang.IllegalStateException: zookeeper not connected

at org.apache.dubbo.remoting.zookeeper.curator.CuratorZookeeperClient.<init>(CuratorZookeeperClient.java:83) ~[dubbo-remoting-zookeeper-2.7.6.jar:2.7.6]

at org.apache.dubbo.remoting.zookeeper.curator.CuratorZookeeperTransporter.createZookeeperClient(CuratorZookeeperTransporter.java:26) ~[dubbo-remoting-zookeeper-2.7.6.jar:2.7.6]

at org.apache.dubbo.remoting.zookeeper.support.AbstractZookeeperTransporter.connect(AbstractZookeeperTransporter.java:70) ~[dubbo-remoting-zookeeper-2.7.6.jar:2.7.6]

at org.apache.dubbo.remoting.zookeeper.ZookeeperTransporter$Adaptive.connect(ZookeeperTransporter$Adaptive.java) ~[dubbo-common-2.7.6.jar:2.7.6]

at org.apache.dubbo.configcenter.support.zookeeper.ZookeeperDynamicConfiguration.<init>(ZookeeperDynamicConfiguration.java:70) ~[dubbo-2.7.6.jar:2.7.6]

at org.apache.dubbo.configcenter.support.zookeeper.ZookeeperDynamicConfigurationFactory.createDynamicConfiguration(ZookeeperDynamicConfigurationFactory.java:37) ~[dubbo-2.7.6.jar:2.7.6]

at org.apache.dubbo.common.config.configcenter.AbstractDynamicConfigurationFactory.lambda$getDynamicConfiguration$0(AbstractDynamicConfigurationFactory.java:39) ~[dubbo-common-2.7.6.jar:2.7.6]

at java.base/java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1705) ~[na:na]

at org.apache.dubbo.common.config.configcenter.AbstractDynamicConfigurationFactory.getDynamicConfiguration(AbstractDynamicConfigurationFactory.java:39) ~[dubbo-common-2.7.6.jar:2.7.6]

at org.apache.dubbo.common.config.configcenter.DynamicConfiguration.getDynamicConfiguration(DynamicConfiguration.java:223) ~[dubbo-common-2.7.6.jar:2.7.6]

at org.apache.dubbo.config.bootstrap.DubboBootstrap.prepareEnvironment(DubboBootstrap.java:857) ~[dubbo-2.7.6.jar:2.7.6]

at org.apache.dubbo.config.bootstrap.DubboBootstrap.startConfigCenter(DubboBootstrap.java:603) ~[dubbo-2.7.6.jar:2.7.6]

at org.apache.dubbo.config.bootstrap.DubboBootstrap.useRegistryAsConfigCenterIfNecessary(DubboBootstrap.java:671) ~[dubbo-2.7.6.jar:2.7.6]

at org.apache.dubbo.config.bootstrap.DubboBootstrap.initialize(DubboBootstrap.java:509) ~[dubbo-2.7.6.jar:2.7.6]

at org.apache.dubbo.config.bootstrap.DubboBootstrap.start(DubboBootstrap.java:740) ~[dubbo-2.7.6.jar:2.7.6]

at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onContextRefreshedEvent(DubboBootstrapApplicationListener.java:59) ~[dubbo-2.7.6.jar:2.7.6]

at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onApplicationContextEvent(DubboBootstrapApplicationListener.java:52) ~[dubbo-2.7.6.jar:2.7.6]

at org.apache.dubbo.config.spring.context.OneTimeExecutionApplicationContextEventListener.onApplicationEvent(OneTimeExecutionApplicationContextEventListener.java:40) ~[dubbo-2.7.6.jar:2.7.6]

at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]

at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]

at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]

at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:403) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]

at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:360) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]

at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:897) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]

at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:553) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]

at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]

at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]

at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]

at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]

at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]

at com.bjsxt.provider.ProviderApplication.main(ProviderApplication.java:11) ~[classes/:na]

Caused by: java.lang.IllegalStateException: zookeeper not connected

at org.apache.dubbo.remoting.zookeeper.curator.CuratorZookeeperClient.<init>(CuratorZookeeperClient.java:80) ~[dubbo-remoting-zookeeper-2.7.6.jar:2.7.6]

... 30 common frames omitted

为什么一直连不上？？？？？？？？ 这个报错什么意思？

老师，这是我对servlet的一些理解，麻烦您帮我看下理解的对错。

        在这个视频中，idea通过Tomcat下的catalina.sh，创建了该项目的副本Tomcat

        在副本Tomcat下，有localhost的host配置项。

//for循环删除
for (int i=0;i<list.size();i++){
    list.remove(i);
}

//迭代器删除
for(Iterator<String> it = list.iterator();it.hasNext();){
    it.next();
    it.remove();
}

问题：使用迭代器删除元素时，iterator.remove()方法执行过程中，list数组是没有做动态变化的吧?

在list.remove()执行过程中list数组有做动态变化，所以出现在for循环中调用list.remove()删除全部元素时，无法删除干净的情况。

如果使用迭代器删除元素时，list数组动态变化了，而游标的位置又不变，那么也会出现无法删除干净的情况。

这里所说的重写时子类对应方法的返回值类型要小于父类，Horse是Vehicle的子类，从大小关系上是Vehicle大Horse小吗？那为什么会说子类包含父类的说法（子类可以派生新的属性和方法）？ 不是很理解大小是从什么角度定义的。

1. 这里静态动态有点蒙圈.....

2. 听的不是很有思路.....

$(function(){
	// ********************************全选实现操作***************************************
	// $("#chks").click(function(){
	// 	// 全选是否被选中(返回true或者false)
	// 	var flag = $("#chks").prop("checked");
	// 	// 操作其他的多选
	// 	$("input[name = 'chk']").prop("checked",flag);
	// })
	 $("#chks").click(function(){
				  	   	
				  	   	  var  flag= $("#chks").prop("checked");
				  	   	  
				  	   	  $("input[name='chk']").prop("checked",flag);
				  	   })
})

	<head>
		<meta charset="utf-8">
		<title></title>
		<!--声明css代码域-->
		<style type="text/css">
			tr{
				height: 40px;
			}
		</style>
		<script src="js/demo1.js" type="text/javascript" charset="UTF-8"></script>
		
		<script src="js/jquery-1.9.1.js" type="text/javascript" charset="UTF-8"></script>
	</head>

demo1.js:1 Uncaught ReferenceError: $ is not defined

    at demo1.js:1

(anonymous) @ demo1.js:1

第一行$直接就报错未定义，和视频里老师写的一样啊？？？

我调用方法往redis中添加的数据用postman验证没问题，为啥用前端页面测试就不行了呢？

老师，Person implements Serializable，有行private static final long serialVersionUID = -3654329494598536934L;这个怎么回事，不加就报错

为什么没数据错乱？

package cn.sxt.thread2;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Test1 {
	public static void main(String[] args){
		//(1)创建一个线程池，线程池中只有一个线程对象
		ExecutorService pool1 = Executors.newSingleThreadExecutor();
		//（2）创建一个线程池，线程池中有线程的数量固定
		//ExecutorService pool1 = Executors.newFixedThreadPool(10);
		//（3）创建一个线程池，线程池中的数量可以动态的改变
		//ExecutorService pool1 = Executors.newCachedThreadPool();
		/**使用线程池执行大量的Runnable命令*/
		for(int i=0;i<20;i++){
			final int n=i;
			Runnable command = new Runnable() {
				public void run(){
					System.out.println("开始执行："+n);
					try {
						Thread.sleep(2000);
					} catch (InterruptedException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				
				System.out.println("执行结束："+n);
			}
		};//任务结束			
		//将任务交给线程池中的线程去执行
		pool1.execute(command);
	}
	//关闭线程池
	pool1.shutdown();
   }

}

我指定的路径怎么全红啊老师，帮我看一下哪里没有设置对吗？settings.xml也是用的老师的复制到.m2目录下的。

多路io复用是不是就相当于A0-A7的端口不够用的时候复用A8-A15的端口，然后A8-A5这些端口自己还有其他的功能。

net stop MySQL80，服务名称MySQL80是怎么确定的？我不知道我的计算机上服务名称是什么

怎么实现x、y的格式化，还是加f吗还是别的

老师，我有zc用户和root用户，为啥我在/home目录中找不到对应的目录呢？