问题：请问老师，我使用的是idea，jdk13.0.2，这个版本后续操作会存在什么问题吗，长远考虑，我有没有必要安装7或8等等一些低版本的jdk备用呢
这章的都才去哪下载？找了老半天没找到，请老师给个链接
这边内网映射失败了呢
laoshizhegeshizahuishiya
这个react 后台管理系统，怎么能用学习资料里面的代码直接跑起来，我现在跑起来页面没有数据，服务端报错504
老师你给的删除代码只能删除一条数据，如果我想要按条件删除或者删除全部时难道一定要通过for循环遍历去删除吗？
xiaoshuo.rar
老师麻烦帮我看下为什么会爬取失败，只爬取了一点。。。。
老师我想从s数组角标为1的值开始，复制到sBak角标1的地方，打印的结果应该是：null 尚学堂 百度 京东 腾讯，null 但是这里运行为什么会报错啊，是我语法写的不对吗
构造方法会自动调用吗？还是跟普通方法一样得手动调用呢？记得有个方法可以自动调用呢，但是忘记是哪个了
string string1 = scanner.next（）;
这个是将什么内容赋值给string1？
老师，请问在返回Bullet的时候为什么要在后面加（self）呢？
难道是版本不对么？
代码:
import re pattern="(\d+$)-(\d{8,10}$)" s="010-980451762" v=re.match(pattern,s) print(v)
问题:
老师请问一下，我在pattern的两个分组中都加了结尾符$，这个时候返回的结果是None，为什么我把结尾符去了就可以匹配了呢?麻烦老师给我解释一下里面的原因?
老师我打开这个网址显示错误，然后找到下载的版本都需要花钱，是我找的方式不对么。
老师帮忙看看这个报错
服务器报错信息
24-Feb-2021 19:34:06.220 严重 [http-nio-8080-exec-5] org.apache.catalina.core.StandardWrapperValve.invoke 在路径为/webdemo_war的上下文中，Servlet[com.example.webdemo.web.servlet.UserLoginServlet]的Servlet.service（）引发了具有根本原因的异常Servlet执行抛出一个异常 java.util.MissingResourceException: Can't find bundle for base name db, locale zh_CN at java.base/java.util.ResourceBundle.throwMissingResourceException(ResourceBundle.java:2055) at java.base/java.util.ResourceBundle.getBundleImpl(ResourceBundle.java:1689) at java.base/java.util.ResourceBundle.getBundleImpl(ResourceBundle.java:1593) at java.base/java.util.ResourceBundle.getBundleImpl(ResourceBundle.java:1556) at java.base/java.util.ResourceBundle.getBundle(ResourceBundle.java:857) at com.example.webdemo.commons.JdbcUtils.<clinit>(JdbcUtils.java:14) at com.example.webdemo.dao.impl.UserLoginDaoImpl.selectUsersByUserNameAndUserPwd(UserLoginDaoImpl.java:17) at com.example.webdemo.service.impl.UserLoginServiceImpl.userLogin(UserLoginServiceImpl.java:14) at com.example.webdemo.web.servlet.UserLoginServlet.doPost(UserLoginServlet.java:30) at javax.servlet.http.HttpServlet.service(HttpServlet.java:652) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:346) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:887) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1684) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.base/java.lang.Thread.run(Thread.java:832) 24-Feb-2021 19:34:10.829 严重 [http-nio-8080-exec-6] org.apache.catalina.core.StandardWrapperValve.invoke 在路径为/webdemo_war的上下文中，Servlet[com.example.webdemo.web.servlet.UserLoginServlet]的Servlet.service（）引发了具有根本原因的异常Servlet执行抛出一个异常 java.lang.NoClassDefFoundError: Could not initialize class com.example.webdemo.commons.JdbcUtils at com.example.webdemo.dao.impl.UserLoginDaoImpl.selectUsersByUserNameAndUserPwd(UserLoginDaoImpl.java:17) at com.example.webdemo.service.impl.UserLoginServiceImpl.userLogin(UserLoginServiceImpl.java:14) at com.example.webdemo.web.servlet.UserLoginServlet.doPost(UserLoginServlet.java:30) at javax.servlet.http.HttpServlet.service(HttpServlet.java:652) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:346) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:887) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1684) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.base/java.lang.Thread.run(Thread.java:832) 24-Feb-2021 19:35:33.939 严重 [http-nio-8080-exec-8] org.apache.catalina.core.StandardWrapperValve.invoke 在路径为/webdemo_war的上下文中，Servlet[com.example.webdemo.web.servlet.UserLoginServlet]的Servlet.service（）引发了具有根本原因的异常Servlet执行抛出一个异常 java.lang.NoClassDefFoundError: Could not initialize class com.example.webdemo.commons.JdbcUtils at com.example.webdemo.dao.impl.UserLoginDaoImpl.selectUsersByUserNameAndUserPwd(UserLoginDaoImpl.java:17) at com.example.webdemo.service.impl.UserLoginServiceImpl.userLogin(UserLoginServiceImpl.java:14) at com.example.webdemo.web.servlet.UserLoginServlet.doPost(UserLoginServlet.java:30) at javax.servlet.http.HttpServlet.service(HttpServlet.java:652) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:346) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:887) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1684) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.base/java.lang.Thread.run(Thread.java:832) 24-Feb-2021 19:35:40.832 严重 [http-nio-8080-exec-9] org.apache.catalina.core.StandardWrapperValve.invoke 在路径为/webdemo_war的上下文中，Servlet[com.example.webdemo.web.servlet.UserLoginServlet]的Servlet.service（）引发了具有根本原因的异常Servlet执行抛出一个异常 java.lang.NoClassDefFoundError: Could not initialize class com.example.webdemo.commons.JdbcUtils at com.example.webdemo.dao.impl.UserLoginDaoImpl.selectUsersByUserNameAndUserPwd(UserLoginDaoImpl.java:17) at com.example.webdemo.service.impl.UserLoginServiceImpl.userLogin(UserLoginServiceImpl.java:14) at com.example.webdemo.web.servlet.UserLoginServlet.doPost(UserLoginServlet.java:30) at javax.servlet.http.HttpServlet.service(HttpServlet.java:652) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:346) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:887) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1684) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.base/java.lang.Thread.run(Thread.java:832) 24-Feb-2021 19:35:49.856 严重 [http-nio-8080-exec-10] org.apache.catalina.core.StandardWrapperValve.invoke 在路径为/webdemo_war的上下文中，Servlet[com.example.webdemo.web.servlet.UserLoginServlet]的Servlet.service（）引发了具有根本原因的异常Servlet执行抛出一个异常 java.lang.NoClassDefFoundError: Could not initialize class com.example.webdemo.commons.JdbcUtils at com.example.webdemo.dao.impl.UserLoginDaoImpl.selectUsersByUserNameAndUserPwd(UserLoginDaoImpl.java:17) at com.example.webdemo.service.impl.UserLoginServiceImpl.userLogin(UserLoginServiceImpl.java:14) at com.example.webdemo.web.servlet.UserLoginServlet.doPost(UserLoginServlet.java:30) at javax.servlet.http.HttpServlet.service(HttpServlet.java:652) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:346) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:887) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1684) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.base/java.lang.Thread.run(Thread.java:832)
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