这里为什么用double来命名变量 final double是什么意思啊

老师，安装包在哪里

老师问下图片中的报错是因为啥？两次Test测试都报这个错误。

两次选中图片中蓝色的后续也正常 运行。

get和set方法那个快捷键是啥？忘了

飞机可以运行,但是IDEA终端在按键时背景报错

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "com.bjsxt.Shell.drawMySelf(java.awt.Graphics)" because "this.shells[i]" is null

at com.bjsxt.MyGameFrame.paint(MyGameFrame.java:104)

at java.desktop/sun.awt.RepaintArea.paintComponent(RepaintArea.java:264)

at java.desktop/sun.lwawt.LWRepaintArea.paintComponent(LWRepaintArea.java:59)

at java.desktop/sun.awt.RepaintArea.paint(RepaintArea.java:240)

at java.desktop/sun.lwawt.LWComponentPeer.handleJavaPaintEvent(LWComponentPeer.java:1310)

at java.desktop/sun.lwawt.LWComponentPeer.handleEvent(LWComponentPeer.java:1191)

at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5056)

at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2324)

at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2780)

at java.desktop/java.awt.Component.dispatchEvent(Component.java:4827)

at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:775)

at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:720)

at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:714)

at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)

at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)

at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:97)

at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:747)

at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)

at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)

at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)

at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:744)

at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)

at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)

at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)

at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)

at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)

at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

2022-12-25 19:46:49.339 java[93394:8193097] TSM AdjustCapsLockLEDForKeyTransitionHandling - _ISSetPhysicalKeyboardCapsLockLED Inhibit

飞机这个可以运行,但是IDEA终端按键时报红字

这是什么原因导致的？

为什么没有办法用for-each遍历，报错

public static void main(String[] args) {
    MyStack<String> a = new MyStack<>();
    a.push("a");
    a.push("b");
    a.push("c");
    a.push("D");
    a.push("F");
    System.out.println(a.size);
    System.out.println(a.empty());
    System.out.println(a.pop());
    System.out.println(a.pop());
    System.out.println(a.pop());
    for (String b:a){

    }
    }
}

课上讲的txt文件可以发一下嘛？谢谢

老师 正则表达式里面的$是开头还是结尾啊？

视频中添加注解的快捷方式是啥？

老师，为什么会加载不了vant组件？

index.js文件

Page({

  data: {

   show: false

   },

  onClickShow() {

   this.setData({ show: true });

   },

  onClickHide() {

   this.setData({ show: false });

   },

 });

为什么会引入组件失败呢？

老师 ，上一节不是卸载了mysql吗？为什么还存在进程？

采取第二种方法，使用自己的服务器，但是打印结果是登录失败，如何解决呢？