Java: How to import a variable in another file?

Question

Please read the bottom before doing anything (but it might be long)

I am trying to make a text-based Minecraft Server, and I'm having trouble in Mines.java. I want to import the integer 'money' into [you'll see the 7-slash comments] in Mines.java, from Main.java. I tried import [package].Main.main.money, but that didn't work.

I am using Mars.1 Eclipse.

Main.java

// NOTE: Please read 'cc.txt' in src folder before modifying

package com.quaggles.main;

import java.util.Scanner;

public class Main {
    // System.out.println(""); (to copy)
    // System objects
    static boolean running = true;
    static Scanner in = new Scanner(System.in);
    static String input;
    static String username;
    // Game variables
    static int coins = 100;
    static int level = 1;
    // Methods that may come in handy
    public static void PETC() {
        System.out.println("Press enter to continue...");
        try {
            System.in.read();
        } catch (Exception e) {
            // Handle any exceptions
        }
    }
    // Doesn't work in java console (sorry Eclipse users) (still testing)
    public static void clearConsole() {
        try {
            final String os = System.getProperty("os.name");

            if (os.contains("Windows")) {
                Runtime.getRuntime().exec("cls");
            } else {
                Runtime.getRuntime().exec("clear");
            }
        } catch (final Exception e) {
            // Handle any exceptions
        }
    }

    public static void main(String[] args) {
        USER: while (running) {
            System.out.println("What is your username:");
            input = in.nextLine();
            if (input.equals("")) {
                System.out.println("You typed nothing! Please try again.");
                PETC();
                clearConsole();
                continue USER;
            } else {
                username = input;
                break USER;
            }
        }
        clearConsole();
        System.out.println("Running on " + System.getProperty("os.name") + "\n");
        System.out.println("Welcome to...");
        System.out.println("   _____                           _____            __ _");
        System.out.println("  / ____|                         / ____|          / _| |");
        System.out.println(" | (___   ___ _ ____   _____ _ __| |     _ __ __ _| |_| |_");
        System.out.println("  \\___ \\ / _ \\ '__\\ \\ / / _ \\ '__| |    | '__/ _` |  _| __|");
        System.out.println("  ____) |  __/ |   \\ V /  __/ |  | |____| | | (_| | | | |_");
        System.out.println(" |_____/ \\___|_|    \\_/ \\___|_|   \\_____|_|  \\__,_|_|  \\__|\n");
        System.out.println("    v0.0.1 beta");
        System.out.println("------------------------------------------");
        System.out.println("ServerCraft is a project made by Quaggle\n" + "that tries to answer the question:\n"
                + "What if a Minecraft server was text based?");
        System.out.println("------------------------------------------\n");
        PETC();
        clearConsole();
        System.out.println("------------------------------------------");
        GAME: while (running) {
            input = in.nextLine().toLowerCase();
            if (input.equals("exit")) {
                break GAME;
            } else if (input.equals("help")) {
                clearConsole();
                System.out.println("HELP");
                System.out.println("------------------------------------------");
                System.out.println("help - shows all* commands");
                System.out.println("stats - shows your stats");
                System.out.println("updates - show any updates on the game");
                System.out.println("mine - go to the mines");
                System.out.println("home");
                System.out.println("exit - quits the game :(\n");
                System.out.println("*not actually all - find them out yourself ;)");
                PETC();
                clearConsole();
                continue GAME;
            } else if (input.equals("stats")) {
                System.out.println("STATISTICS");
                System.out.println("------------------------------------------");
                System.out.println("Coins: " + coins);
                System.out.println("Level " + level);
                PETC();
                clearConsole();
                continue GAME;
            } else if (input.equals("updates")) {
                System.out.println("UPDATES");
                System.out.println("------------------------------------------");
                System.out.println("");
                System.out.println("1-8-16 - PRECIOUS");
                System.out.println("Added mining and a money system\n");
                System.out.println("1-7-16 - Mr. Krabs! I have an idea!");
                System.out.println("I finally started working on the game after countless reconsiderations & regrets!");
            } else if (input.equals("mine")) {
                com.quaggles.main.Mines.mine();
            } else {
                System.out.println("\'" + input + "\' is not a command.");
            }
        }
        System.out.println("Thanks for playing, " + username + "!");
        PETC();
        System.exit(0);
    }
}

Mines.java

// NOTE: Please read 'cc.txt' in src folder before modifying
// WORK IN PROGRESS: I am still working on this, (may be very buggy)

package com.quaggles.main;

import java.util.Scanner;

import com.quaggles.main.Main.*; //unneeded at the moment

public class Mines {
    // System objects
    static boolean running = true;
    static Scanner in = new Scanner(System.in);
    static String input;
    /////// Import 'money' from Main.java
    static int pickaxe = 1;
    static int pickaxeXP = 0;
    static int pickaxeLevelUp = 100;
    // Game variables
    public static void mine() {
        GAME: while (running) {
            System.out.println("Welcome to the...");
            System.out.println("  __  __ _                 ");
            System.out.println(" |  \\/  (_)                ");
            System.out.println(" | \\  / |_ _ __   ___  ___ ");
            System.out.println(" | |\\/| | | '_ \\ / _ \\/ __|");
            System.out.println(" | |  | | | | | |  __/\\__ \\");
            System.out.println(" |_|  |_|_|_| |_|\\___||___/");
            System.out.println("------------------------------------------");
            System.out.println("Type \'mine\' to start mining");
            input = in.nextLine();
            if (input.equals("mine")) {
                /////// money
            }
        }
    }
}

EDIT: I just realized 'money' doesn't exist and I forgot I renamed it to 'coins', that should clear up any confusion.

Ok, i'll try and be as in-depth as possible.

Some person said on my 'how to execute another file thing' that maybe I should take a java programming course and not learn a programming language by Stack Overflow, and I respect that.

I just wanna make this clear, I like to learn things my own special way. I'm 11, and from my perspective, all the courses on youtube either explain things too slowly that by episode 11 we will be still learning about integer, or they move into things too quickly. And the ones that aren't on youtube cost money, so don't recommend me anything, It's fine. Besides, you don't have to answer. Thank you whoever that was.

Answer 1

I'll answer your specific question as best as possible first. There is no variable named money in the class com.quaggles.main.Main but there is a coins variable so if that's the variable you mean, here's how:

Mines.java:

        if (input.equals("mine")) {
            System.out.println("My coins are: " + Main.coins);
        }

Note 1: classes in the same Java package (i.e. namespace) do not need to import, nor do they need to fully specify the namespace, so you can simply reference Main and Mines (i.e., without the namespace com.quaggles.main).

Note 2: since Main.coins is static there is only a single instance of this coins in the server; presumably, that means the server can only handle one player.

Note 3: Main calls Mines.mines() and Mines then calls Main.coins -- this is called a circular reference. As professionals, we work hard to avoid circular references because they can cause unpredictable behavior. Consider refactoring your code, perhaps to include a list of Accounts, i.e., one for each player which contains the coins or money.

Good luck with your learning, and don't get discouraged by negative comments.