官网上和很多教程上都是说推荐在application中初始化ARouter，但是不清楚这段代码应该贴在哪里，什么是application？

if (isDebug()) {           // These two lines must be written before init, otherwise these configurations will be invalid in the init process
   ARouter.openLog();     // Print log
   ARouter.openDebug();   // Turn on debugging mode (If you are running in InstantRun mode, you must turn on debug mode! Online version needs to be closed, otherwise there is a security risk)
}
ARouter.init(mApplication); // As early as possible, it is recommended to initialize in the Application