trying to collect data from other classes to send to server

This is my first android program ever I usually code in python... I've watch a ton of java tutorials but Java is so different  I'm having trouble ...so here is what I need to do... I have my Main class and it collects user input  and returns the variable public string username and public string password then I have a gps Class and it return the variable public double longituts and public double latitude... in python I would make these global variable(ie self.username ... etc ) collect the data into in a method and send it to the server in mysql format... I have a new class  and Its called GetdataandSend

public calss GetdataandSend(){
I want to collect the variables from my Main Class and gps class
store the variables and then send to the server the data (using Mysql fomat) 
}

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can some one point me in a direction of some titorials or examples of this ... thanks