Scanner scanner = new Scanner(System.in);

这句怎么理解呢？

老师我还是不理解为什么要用线程同步，如果已经放满了，push方法发while不是会一直循环，防止再次放入，如果已经取空了，pop的while也会一直循环，直到另一个线程修改index的时候会跳出自己的while循环，不是吗

我想到的只能是缓冲区空的时候，取线程一直while，然后直到存线程放入后，但是还没来得及修改index，就切换到取线程，此时index没有变化，实际有馒头了，但是等下次轮询index就会更新，这也只是减慢了效率，不会影响取线程异常，我想不到其他异常情况了

求老师点拨一下

A的ID 最终是 10的地址还是 列表四个组合的新地址？？

用pycharm运行代码，结果fidder上面抓不到相应的包，配置我是按照教程进行的

老师您好，在子类里写rest();是啥意思？就算我不写我一样可以直接用这个方法啊，老师写在这里只是想要告诉我们子类可以直接继承父类的普通方法吗

SpringBoot整合JSP，页面无法访问。。。。。。。。。。。。。

老师你好，第6章108节重写str方法的视频第1分55秒，返回了return语句里的话就要打印出来这个理解，那下边的s = str(p)为什么只打印print("重写__str__方法")，而不打印return语句里的内容了呢？视频里老师说返回给变量s了，不太明白为什么第一次的返回就可以打印，第二次返回给变量就不打印了？

 是我记错了么 抽象类好像不能用new来实例化抽象类的

老师，为什么分数不显示出来？

public class Welcome {
               public static void main(String[] args){
                               System.out.println("hello world!");
               }
}

老师 在运行时出现了这样子的情况

D:\Mycode>javac Welcome.java

Welcome.java:1: 错误: 进行语法分析时已到达文件结尾

public class Welcome

                    ^

1 个错误

如何在maven中央仓库，查看starter所支持的springboot的版本？

老师，我这边接口serviceapi，provider01，provider02 都启动正常

2020-07-07 17:04:11.963 ERROR 15980 --- [nfoReplicator-0] c.n.d.s.t.d.RedirectingEurekaHttpClient  : Request execution error. endpoint=DefaultEndpoint{ serviceUrl='http://localhost:8085/eureka/}

com.sun.jersey.api.client.ClientHandlerException: java.net.ConnectException: Connection refused: connect

at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187) ~[jersey-apache-client4-1.19.1.jar:1.19.1]

at com.sun.jersey.api.client.filter.GZIPContentEncodingFilter.handle(GZIPContentEncodingFilter.java:123) ~[jersey-client-1.19.1.jar:1.19.1]

at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27) ~[eureka-client-1.9.13.jar:1.9.13]

at com.sun.jersey.api.client.Client.handle(Client.java:652) ~[jersey-client-1.19.1.jar:1.19.1]

at com.sun.jersey.api.client.WebResource.handle(WebResource.java:682) ~[jersey-client-1.19.1.jar:1.19.1]

at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74) ~[jersey-client-1.19.1.jar:1.19.1]

at com.sun.jersey.api.client.WebResource$Builder.post(WebResource.java:570) ~[jersey-client-1.19.1.jar:1.19.1]

at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.register(AbstractJerseyEurekaHttpClient.java:56) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.MetricsCollectingEurekaHttpClient.execute(MetricsCollectingEurekaHttpClient.java:73) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.executeOnNewServer(RedirectingEurekaHttpClient.java:118) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.execute(RedirectingEurekaHttpClient.java:79) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:120) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:847) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101) [eureka-client-1.9.13.jar:1.9.13]

at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_231]

at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_231]

at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_231]

at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_231]

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_231]

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_231]

at java.lang.Thread.run(Thread.java:748) [na:1.8.0_231]

Caused by: java.net.ConnectException: Connection refused: connect

at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method) ~[na:1.8.0_231]

at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85) ~[na:1.8.0_231]

at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_231]

at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_231]

at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_231]

at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) ~[na:1.8.0_231]

at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_231]

at java.net.Socket.connect(Socket.java:606) ~[na:1.8.0_231]

at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:121) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:134) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:605) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:440) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:118) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) ~[httpclient-4.5.10.jar:4.5.10]

at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:173) ~[jersey-apache-client4-1.19.1.jar:1.19.1]

... 30 common frames omitted

2020-07-07 17:04:11.964  WARN 15980 --- [nfoReplicator-0] c.n.d.s.t.d.RetryableEurekaHttpClient    : Request execution failed with message: java.net.ConnectException: Connection refused: connect

2020-07-07 17:04:11.967  WARN 15980 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_CONSUMER-FEIGN/DESKTOP-8NIQN7P:consumer-feign:8083 - registration failed Cannot execute request on any known server

com.netflix.discovery.shared.transport.TransportException: Cannot execute request on any known server

at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:112) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:847) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101) [eureka-client-1.9.13.jar:1.9.13]

at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_231]

at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_231]

at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_231]

at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_231]

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_231]

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_231]

at java.lang.Thread.run(Thread.java:748) [na:1.8.0_231]

老师，为什么我按照您的代码写但是最后炮弹还是出一点边界啊？

package com.bjsxt;

import java.awt.*;

/**
 * 炮弹类
 */
public class Shell extends GameObject {
    double degree;//角度，炮弹沿着任意角度飞行

    public Shell(){
        x=200;
        y=200;

        degree = Math.random()*Math.PI*2;

        width = 10;
        height = 10;

        speed = 7;
    }

    @Override
    public void drawMyself(Graphics g) {
        Color c = g.getColor();
        g.setColor(Color.yellow);
        g.fillOval((int)x,(int)y,width,height);
        g.setColor(c);
        //super.drawMyself(g);

        //根据自己的算法指定移动的路径
        x += speed*Math.cos(degree);
        y += speed*Math.sin(degree);

        //碰到边界改变方向
        if (y>Constant.Game_HEIGHT-this.height||y<40){
            degree=-degree;
        }
        if (x>Constant.Game_WIDTH-this.width||x<0){
            degree = Math.PI-degree;
        }

    }
}

<template>
  <div>
    <div class="banner">用户登录注册</div>
    <el-card class="box-card">
      <el-tabs stretch v-model="activeName" @tab-click="clickHandle">
        <el-tab-pane label="登录" name="login">
          <el-form
            :model="loginForm"
            status-icon
            ref="loginForm"
          >
            <el-form-item label="账号" >
              <el-input type="text" v-model="loginForm.username" ></el-input>
            </el-form-item>
             <el-form-item label="账号" >
              <el-input type="password" v-model="loginForm.password" ></el-input>
            </el-form-item>
           
          </el-form>
        </el-tab-pane>
        <el-tab-pane label="注册" name="register">注册账号</el-tab-pane>
      </el-tabs>
    </el-card>
  </div>
</template>

<script>
export default {
  data() {
    return {
      activeName: "",
      loginForm: {
        username: "",
        password: ""
      }
    };
  },
  methods: {
    clickHandle(tab, event) {
      console.log(tab, event);
    }
  }
};
</script>

<style scoped>
.banner {
  font: 30px;
  margin-top: 100px;
}
.box-card {
  margin: 0 auto;
  margin-top: 20px;
  width: 600px;
}
</style>

老师我表单为啥不显示  没报错啊