stage
stage其实就是一个窗口，它啥也不是，打开所有windows的程序都会有一个窗口，这个窗口就是javafx里的stage。里面的内容不属于stage，stage就是一个窗口，就这么简单。
Stage is actually a window. It is nothing. All windows programs will have a window when they are opened. This window is the stage in javafx. The content inside does not belong to the stage, the stage is a window, it’s that simple.
package com.jx