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Java methods and classes, how are they combined?

I am currently writing a program for an introductory Java class. I have two pieces of my puzzle. Hopefully this is a relatively simple answer.

First, this is what I am trying to use as my main program:

import java.util.Scanner;

public class TheATMGame
{
 public static void main(String[] args){


    Scanner input = new Scanner(System.in);


    double newBalance = 0;
    double monthlyInterest = 0;
    int answer = 0;


    int i=1;
    while (i < 100) {
        System.out.print ("Please enter your ID: ");
        answer = input.nextInt();
        System.out.println(" ");
        if (answer >=0 && answer<10) 
        TheATMGame.runGame (answer);
        else
         System.out.println("Sorry, this ID is invalid.");
     }
    }


    public static void runGame(int id) {
      double amount = 0;
      int continueOn = 0;
      while (continueOn < 4) {
        ATMGame myATM = new ATMGame();
        Scanner input = new Scanner(System.in);
        System.out.println ("---Main menu--- ");
        System.out.println ("1: Check balance ");
        System.out.println ("2: Withdraw ");
        System.out.println ("3: Deposit ");
        System.out.println ("4: exit ");

        int answer = input.nextInt();

        if (answer == 1)
            System.out.println("your balance is: " + myATM.getBalance (id));
        else if (answer == 2){
            System.out.println("Enter an amount to withdraw: ");
            amount = input.nextInt();
            myATM.withdraw(amount, id);
        }
        else if (answer == 3)
{
            System.out.println("Enter an amount to deposit: ");
            amount = input.nextInt();
            myATM.deposit(amount, id);
        }
        else if (answer == 4)
            continueOn = 4;
        else if (answer > 4)
            System.out.println ("Please review the main menu. " +
                    "Your selection must be between 1-4.");
      }
    }

//ATM class (balance, annualInterestRate2, id2)
//ATM myATM = new ATM (20000, 4.5, 1122 );
//newBalance = myATM.withdraw(2500);
//newBalance = myATM.deposit(3000);
//monthlyInterest = myATM.getMonthlyInterestRate();
//System.out.println("Your current balance is: " + newBalance);
//System.out.println ("Your monthly interest rate is: " +  monthlyInterest);



}

Now, here are all the classes that I want to implement in this program:

import java.util.Date;

public class ATMGame  {

    private double annualInterestRate = 0;
    private double balance = 0;
    private int id = 11;
    private int[] ids = {0,1,2,3,4,5,6,7,8,9};
    private int[] balances = {100,100,100,100,100,100,100,100,100,100};
    public Date dateCreated;


    public ATMGame() {

    }
    public ATMGame (double balance2, double annualInterestRate2, int id2) {
        balance = balance2;
        annualInterestRate = annualInterestRate2;
        id = id2;
        dateCreated.getTime();
    }


    public double getMonthlyInterestRate() {
        double monthlyInterest = annualInterestRate/12;
        return monthlyInterest;
    }


    public double withdraw(double amountWithdrawn, int id) { //This method withdraws money from the account

        double newBalance = balances[id] - amountWithdrawn;
        System.out.println("Your withdrawel has processed. New balance: " + newBalance);
        balances[id] = (int) newBalance;
        return newBalance ;

    }


    public double deposit(double amountDeposited, int id) { //This method deposits money in the account
        double newBalance = balances[id] + amountDeposited;
        System.out.println("Your deposit has processed. New Balance is: " + newBalance);
        balances[id] = (int) newBalance;
        return newBalance ;

    }

    public double getBalance(int id) {
        double myBalance = balances[id];
        balance = myBalance;
        return myBalance ;
    }


}

When I try to run the first program, it says "No main classes". As you can see, I wrote the line "public void Main () ..." to take care of this, but it doesn't seem to work. What am I doing wrong?

Replacing "public void Main () {" with "public static void main (String [] args) {" still returns the error: "No main classes found." : /

http://img21.imageshack.us/img21/9016/asdfsdfasdfg.jpg

I managed to fix this by changing Main.java to TheATMGame.java and then running from ATMGame.java.

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5 answers


In your class, ATMGame

replace the following:

public void Main() {

from:

public static void main(String[] args) {

Also, since this method must be static, you need to change the following:

if (answer >=0 && answer<10)
     runGame (answer);
 else


from:

if (answer >=0 && answer<10)
     ATMGame.runGame (answer);
 else

Then finally you need to change the method signature rungame

, also static. Change it:

public void runGame(int id) {

at

public static void runGame(int id) {
+1


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You must use:

public static void main(String[] args)


Instead of Main, because the JVM calls this method first. This is an agreement.

+3


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You just misidentified the main one. Should be:

public static void main(String[] args) {
    ....
}

However, you will run into some other problems with your code. With a quick glance ...

  • Your main function () is a function and also runGame () - shouldn't be defined elsewhere.
  • You cannot name your two classes the same - call the main () class with something other than ATMGame.
  • Not sure where you are going from ATM class (balance, annualInterestRate2, id2)

    , but this is not valid Java.
+3


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Your method signature should be:

public static void main(String[] args) {
 ...
}

This is the convention that you must follow. Anything else won't work.

+3


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Your public class names must match the file names. This does not apply to your screenshot. Also make sure everything compiles correctly and then try again (using the public static void main (String [] args method) {...}).

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