Thread: Having trouble understanding object relationships and using them correctly?

I have an assignment where you need to transfer money from one account to the other account... using objects of course. So far I have three different files...but I'm getting a class/enum error.

import java.util.Scanner; import java.text.NumberFormat;   public class accountTest{    	public static void main(String[] args){	Scanner input = new Scanner(System.in);	Scanner input2 = new Scanner(System.in);	Scanner input3 = new Scanner(System.in);	Scanner input4 = new Scanner(System.in);	Scanner input5 = new Scanner(System.in);	NumberFormat formatter = NumberFormat.getCurrencyInstance();	System.out.println("Please enter your account balance: ");	double balance = input.nextDouble();	Account mark = new Account(balance);	Account joe = new Account(500);  	System.out.println("Your account balance is: " + formatter.format(mark.getAccountBalance()));  	System.out.println("Please enter the amount you want to deposit into the account: ");	double deposit = input2.nextDouble();	System.out.println("The amount you are depositing is: " + formatter.format(deposit));  	mark.enterDeposit(deposit);  	System.out.println("Your account balance is: " + formatter.format(mark.getAccountBalance()));  	System.out.println("Please enter the amount you want to withdraw: ");	double withdrawal = input3.nextDouble();  	System.out.println("The amount you are withdrawing is: " + formatter.format(withdrawal));  	mark.takeWithdrawal(withdrawal);  	System.out.println("Your account balance is: " + formatter.format(mark.getAccountBalance()));  	System.out.println("Please enter the amount you wish to transfer: ");	double transferAmount = input4.nextDouble();	System.out.println("Which account would you like to transfer " + formatter.format(transferAmount) + " to?");	String account = input5.nextLine();    	Transaction trans = new Transaction(mark, joe);	trans.transferMoney(transferAmount, account);  	System.out.println("You transfered " + transferAmount + " to " + account + ".");  	System.out.println("Mark's account balance is now " + formatter.format(mark.getAccountBalance()));	System.out.println("Joe's account balance is now " + formatter.format(joe.getAccountBalance()));      	} }

  public class Account{  	private double balance = 0;  	public Account(double balance){  	this.balance = balance;	}    	public double getAccountBalance(){    	return balance;	}  	public double enterDeposit(double amount){  	balance = balance + amount;    	return balance;	}  	public double takeWithdrawal(double amount){	balance = balance - amount;	return balance;  	}   }

  public class Transaction{    	private Account mark;	private Account joe;	public Transaction(Account mark, Account joe){  	this.mark = mark;	this.joe = joe;      	}  	public void transferMoney(double amount, String account){    	if(account == "joe")	{   mark.takeWithdrawal(amount); joe.enterDeposit(amount);	}   else if(account == "mark"){  	joe.takeWithdrawal(amount);	mark.enterDeposit(amount); }  	}    	}

That's what I have so far... but I'm having trouble with the transaction class. When I tell it to deposit and withdraw it doesn't withdraw or deposit and the amounts in both accounts stay the same. Any help is appreciated!

Your problem is with comparing Strings:
if(account == "joe")
String are objects, therefore when you are comparing for equivalency, you need to use the .equals() method instead of ==
if(account.equals("joe"))

The "normal" way to compare two objects in java is to either:
1. override the .equals() method, in your Account class, that is inherited from the Object class
2. Implement the Comparable Interface (Comparable (Java Platform SE 6)) in your Account class.