老师，守护线程的意思是，如果给哪个线程加上了守护线程，该线程终止 守护线程也同样会终止对吧

package thread;

/**
 * 守护线程（辅助线程）
 * 1、给用户线程添加守护线程
 * 2、守护线程的生命周期会随着用户线程的结束而结束
 */
class Daemon implements Runnable{
    @Override
    public void run() {
        for (int i=0;i<20;i++){
            System.out.println(Thread.currentThread().getName()+" "+i);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}
public class DaemonThread {
    public static void main(String[] args) throws Exception {
        Thread thread=new Thread(new Daemon(),"守护线程");
        //将该线程设置为守护线程
        thread.setDaemon(true);
        thread.start();
        Thread.sleep(1000);
        System.out.println("主线程结束");
    }
}

这个我给主线程加入了守护线程，主线程结束，守护线程就不能在运行了，但是我的还是会运行一下才会停止，如果改变一下守护线程的休眠时间就正确了 这是为啥？

"C:\Program Files\Java\jdk-13.0.2\bin\java.exe" -Dmaven.multiModuleProjectDirectory=C:\Users\yc\IdeaProjects\case\parent\controller "-Dmaven.home=D:\IntelliJ IDEA 2019.3.2\plugins\maven\lib\maven3" "-Dclassworlds.conf=D:\IntelliJ IDEA 2019.3.2\plugins\maven\lib\maven3\bin\m2.conf" "-Dmaven.ext.class.path=D:\IntelliJ IDEA 2019.3.2\plugins\maven\lib\maven-event-listener.jar" "-javaagent:D:\IntelliJ IDEA 2019.3.2\lib\idea_rt.jar=59100:D:\IntelliJ IDEA 2019.3.2\bin" -Dfile.encoding=UTF-8 -classpath "D:\IntelliJ IDEA 2019.3.2\plugins\maven\lib\maven3\boot\plexus-classworlds-2.6.0.jar" org.codehaus.classworlds.Launcher -Didea.version2019.3.2 org.apache.tomcat.maven:tomcat7-maven-plugin:2.2:run

[INFO] Scanning for projects...

[INFO] 

[INFO] ------------------------< com.bjsxt:controller >------------------------

[INFO] Building controller 1.0-SNAPSHOT

[INFO] --------------------------------[ war ]---------------------------------

[INFO] 

[INFO] >>> tomcat7-maven-plugin:2.2:run (default-cli) > process-classes @ controller >>>

[INFO] 

[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ controller ---

[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!

[INFO] Copying 5 resources

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[INFO] 

[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ controller ---

[INFO] Nothing to compile - all classes are up to date

[INFO] 

[INFO] <<< tomcat7-maven-plugin:2.2:run (default-cli) < process-classes @ controller <<<

[INFO] 

[INFO] 

[INFO] --- tomcat7-maven-plugin:2.2:run (default-cli) @ controller ---

[INFO] Running war on http://localhost:8080/

[INFO] Creating Tomcat server configuration at C:\Users\yc\IdeaProjects\case\parent\controller\target\tomcat

[INFO] create webapp with contextPath: 

7月 05, 2021 9:34:11 下午 org.apache.coyote.AbstractProtocol init

信息: Initializing ProtocolHandler ["http-bio-8080"]

7月 05, 2021 9:34:11 下午 org.apache.catalina.core.StandardService startInternal

信息: Starting service Tomcat

7月 05, 2021 9:34:11 下午 org.apache.catalina.core.StandardEngine startInternal

信息: Starting Servlet Engine: Apache Tomcat/7.0.47

7月 05, 2021 9:34:14 下午 org.apache.catalina.core.ApplicationContext log

信息: No Spring WebApplicationInitializer types detected on classpath

7月 05, 2021 9:34:14 下午 org.apache.catalina.core.ApplicationContext log

信息: Initializing Spring root WebApplicationContext

[INFO] Root WebApplicationContext: initialization started

[INFO] Root WebApplicationContext initialized in 1404 ms

7月 05, 2021 9:34:16 下午 org.apache.catalina.util.SessionIdGenerator createSecureRandom

信息: Creation of SecureRandom instance for session ID generation using [SHA1PRNG] took [359] milliseconds.

7月 05, 2021 9:34:16 下午 org.apache.catalina.core.ApplicationContext log

信息: Initializing Spring DispatcherServlet 'springmvc'

[INFO] Initializing Servlet 'springmvc'

[INFO] Completed initialization in 573 ms

7月 05, 2021 9:34:16 下午 org.apache.coyote.AbstractProtocol start

信息: Starting ProtocolHandler ["http-bio-8080"]

[WARNING] No mapping for GET /

7月 05, 2021 9:35:06 下午 org.apache.catalina.core.StandardWrapperValve invoke

严重: Servlet.service() for servlet [springmvc] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.transaction.CannotCreateTransactionException: Could not open JDBC Connection for transaction; nested exception is com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.] with root cause

java.net.ConnectException: Connection timed out: connect

at java.base/sun.nio.ch.Net.connect0(Native Method)

at java.base/sun.nio.ch.Net.connect(Net.java:493)

at java.base/sun.nio.ch.Net.connect(Net.java:482)

at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:588)

at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:339)

at java.base/java.net.Socket.connect(Socket.java:603)

at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:211)

at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:298)

at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2253)

at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2286)

at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2085)

at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:795)

at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44)

at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)

at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)

at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)

at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)

at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:400)

at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:327)

at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:677)

at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:189)

at org.springframework.jdbc.datasource.DriverManagerDataSource.getConnectionFromDriverManager(DriverManagerDataSource.java:155)

at org.springframework.jdbc.datasource.DriverManagerDataSource.getConnectionFromDriver(DriverManagerDataSource.java:146)

at org.springframework.jdbc.datasource.AbstractDriverBasedDataSource.getConnectionFromDriver(AbstractDriverBasedDataSource.java:205)

at org.springframework.jdbc.datasource.AbstractDriverBasedDataSource.getConnection(AbstractDriverBasedDataSource.java:169)

at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:263)

at org.springframework.transaction.support.AbstractPlatformTransactionManager.startTransaction(AbstractPlatformTransactionManager.java:400)

at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:373)

at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:572)

at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:360)

at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:99)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)

at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:95)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)

at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)

at com.sun.proxy.$Proxy39.addUsers(Unknown Source)

at com.bjsxt.web.controller.UsersController.addUsers(UsersController.java:26)

at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.base/java.lang.reflect.Method.invoke(Method.java:567)

at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)

at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)

at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106)

at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879)

at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)

at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)

at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)

at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)

at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)

at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)

at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)

at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)

at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)

at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)

at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)

at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)

at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)

at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)

at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)

at java.base/java.lang.Thread.run(Thread.java:830)

显示我无法链接数据库。但是我任务管理器里面显示我的mySQL服务是正在运行状态。

而且我Navicat也可以正常连接数据库。这里我用的是users3表

alter table dept90 modify(constraint dept90_fk foreign key(d_id) references dept60(id);

视频中使用add,但使用modify也可以呀，

1、如果dept90的d_id这一列没有约束，用add添加约束或modify修改约束都可以，

2、如果dept90的d_id这一列有了约束，只能用modify来修改约束了，

这样理解对吗？

create table emp2(id int primary key ,name varchar(30),seq_num int unique auto_increment);

课程中的约束是系统自动命名的，如果我要给约束命名同时添加一个自动增长，应该怎么写呢

import asyncio
import functools
async def compute(x,y):
    print(f'compute:{x}+{y}...')
    await asyncio.sleep(1)
    return x+y

async def print_sum(x,y):
    # 创建task
    task = asyncio.create_task(compute(x,y))
    # task绑定回调函数
    task.add_done_callback(functools.partial(end,x,y))
    # 释放下cpu的使用
    await asyncio.sleep(0)
    for i in range(100000):
        if i%500 == 0:
            print(i)
            await asyncio.sleep(0.1)

def end(n,m,t):
    print(f'{n}+{m}={t.result()}')

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(print_sum(1,2))
    loop.close()
  
刚才一段代码复制的有问题，以这个为准

asyncio
functools
(xy):
    (xy)
    asyncio.sleep()
    x+y

(xy):
    task = asyncio.create_task(compute(xy))
    task.add_done_callback(functools.partial(endxy))
    asyncio.sleep()
    i ():
        i%== :
            (i)
            asyncio.sleep()

(nmt):
    (nmt.result())

__name__ == :
    loop = asyncio.get_event_loop()
    loop.run_until_complete(print_sum())
    loop.close()

老师我运行之后报这个错误：

Traceback (most recent call last):

  File "E:/pythonStation/Thread/30_协程的基本使用-asyncio的task的用法.py", line 25, in <module>

    loop.run_until_complete(print_sum(1,2))

  File "D:\python\lib\asyncio\base_events.py", line 468, in run_until_complete

    return future.result()

  File "E:/pythonStation/Thread/30_协程的基本使用-asyncio的task的用法.py", line 10, in print_sum

    task = asyncio.create_task(compute(x,y))

AttributeError: module 'asyncio' has no attribute 'create_task'

 这是为什么呢？

中文乱码  百度了好多方法没用 全乱码- -求解 求解

老师好  请问一下为什么写不了文本文件到d盘呢

老师，电话本项目作业，我在operate类的addOpration中添加了ObjectOutputStream，

public void addOperation() {
    TelNoteRegex telNoteRegex=new TelNoteRegex();
    String name=telNoteRegex.nameValidate();
    String age=telNoteRegex.ageValidate();
    String sex=telNoteRegex.sexValidate();
    String telNum=telNoteRegex.telNumValidate();
    String address=telNoteRegex.addressValidate();
    Person person=new Person(name,age,sex,telNum,address);
    this.list.add(person);
    person.setId(this.list.size());
    ObjectOutputStream oos=null;
    try {
        oos=new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream("d:/person.txt",true)));
        oos.writeObject(person);
        oos.flush();
    } catch (IOException e) {
        e.printStackTrace();
    }finally {
        try {
            if (oos!= null) {
                oos.close();
            }
        }catch(Exception e){
                e.printStackTrace();
            }
        }
    }

然后在Operate类创建了一个ObjectInputStream方法，

/**
 * 对象输入流
 * 初始化list
 */
public void ObjectInputStream(){
    ObjectInputStream ois=null;
    try{
        ois=new ObjectInputStream(new BufferedInputStream(new FileInputStream("d:/person.txt")));
        List list=(List<Person>)ois.readObject();
        this.list=list;
    }catch (Exception e){
        e.printStackTrace();
    }finally {
        try{
            if (ois!=null){
                ois.close();
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

再在app类的start方法里调用operate的ObjectInputStream方法，初始化list内的信息，以便下次打开程序时读取之前存储的信息。

public void start(){
    Menu menu=new Menu();
    TelNoteRegex regex=new TelNoteRegex();
    Operate operate=new Operate();
    operate.ObjectInputStream();//初始化Operate中的list
    while (true) {
        menu.mainMenu();
        int item=regex.menuItemValidate(1,6);
        switch (item){
            case 1:operate.addLogic();break;
            case 2:operate.searchLogic();break;
            case 3:operate.modifyLogic();break;
            case 4:operate.deleteLogic();break;
            case 5:operate.orderLogic();break;
            case 6:System.exit(0);  //结束虚拟机

程序运行后有如下报错。

java.io.EOFException
	at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2638)
	at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:3113)
	at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:853)
	at java.io.ObjectInputStream.<init>(ObjectInputStream.java:349)
	at com.wxc.Operate.ObjectInputStream(Operate.java:159)
	at com.wxc.App.start(App.java:28)
	at com.wxc.App.main(App.java:18)

不知道这个思路问题出在哪里。

老师我在用普通装饰器写接口跳转模板文件的时候没有问题，但是用resful写完接口后跳转模板文件，浏览器打开后是网页源代码，不知道错误在哪里，普通装饰器能打开的，两个方法我都写进去了，还有错误截图，麻烦老师看看哪里的问题

像这种方法都必须要添加this.吗，this.表示当前调用它的对象，但是我觉得这种不写也是可以的吧，对结果不影响，好像就get set方法，构造函数，构造函数调用其他构造器，这里面才需要this吧

老师，这个深入与提高没有课件下载吗？我不想花大量时间取做笔记，有的话给个下载地址，谢谢

老师，为什么这里声明ArrayList的时候，要用List<>

List<String> list = new ArrayList<>();

好像其他地方也有这样的，用父类来声明，new 子类。

public static int bumb(int[] a,int value) {
    int low = 0;
    int high = a.length - 1;
    while (low <= high) {
        int mid = (low + high) / 2;
        if (value == a[mid]) {
            return mid;
        }
        if (value < a[mid]) {
            high = mid + 1;
        }
        if (value > a[mid]) {
            low = mid - 1;
        }else{
            return -1;
        }
    }
return -1;
}

老师，我把最下面的return -1 去掉会报错；视频和作业里都只有一个return -1，有点迷糊了