Java: having multiple objects of one class

问题:

I am having an issue where each class has multiple objects, it is a mess of objects being created of each class and I am having errors. The 4 class files are Main, Game, Updates Building, I will show the constructors of each class and hopefully someone can help me show how to create multiple objects of one class. There are variables in game that I need to access from update and building but when I try errors are returned. How do I access the variables in game from both update and building

Main:

public class Main 
{ 

    public static void main(String[] args)
    {
        Game newGame = new Game();

        newGame.setupGame();
        Game.isRunning=true;
        newGame.gameLoop();

    }

}

Game:

import java.util.Scanner;

public class Game {

    private Scanner input;
    private Updates getUpdates;

    public Game(){
        this.input = new Scanner(System.in);
        this.getUpdates = new Updates(this);
    }
int happyness;
double money;
int population = 1000000;

}

Updates

import java.util.Scanner;

public class Updates {

    private Scanner input;

    private Game newGame;

    Building buildBuilding = new Building();

    public Updates(Game newGame){
        this.newGame = newGame;
        this.input = new Scanner(System.in);
    }
}

Building

import java.util.Scanner;

public class Building {

    public Building(){

        this.input = new Scanner(System.in);
    }

    private Scanner input;
}

I want the building class to be able to access the variables in main as well as the update class being able to access the variables in main.

回答1:

[EDITED]

Change in Updates class:

Building buildBuilding;

public Updates(Game newGame){
    this.newGame = newGame;
    this.input = new Scanner(System.in);
    this.buildBuilding = new Building(newGame);
}

You have accidentally called an empty constructor, so

public Building(Game newGame){

        this.input = new Scanner(System.in);
        this.newGame = newGame;
    }

was never called, and therefore input was NULL.