I don't find where I did wrong ...

Hello! I'm currently learning java from a book and made this exercise, the withdraw() and deposit() methods doesn't work, some help please?

here is my code:

Code:

---

package Chapter8;

import java.util.*;

public class Ex8_7 {
        public static void main (String args[]){
               
                Account account = new Account(1122, 20000.0D);
               
                account.setAnnualInterestRate(4.5D);
               
                account.withdraw(2500.0D);
               
                account.deposit(3000.0D);
               
                System.out.print("The balance is "+account.getBalance()+"\n"+"The monthly interest rate is "+account.getMonthlyInterestRate()+"\n"
                                +"The date when this account was created is: "+account.getDateCreated());
               
        }
}

class Account{
       
        private int id;
        private double balance;
        private double annualInterestRate;
        private Date dateCreated = new Date();
       
        Account(){
        }
       
        Account(int newID, double newBalance){
                id = newID;
                balance = newBalance;
        }
       
        public int getID(){
                return id;
        }
       
        public void setID(int newID){
                id = newID;
        }
       
        public double getBalance(){
                return balance;
        }
       
        public void setBalance(double newBalance){
                balance = newBalance;
        }
       
        public double getAnnualInterestRate(){
                return annualInterestRate;
        }
       
        public void setAnnualInterestRate(double newAnnualInterestRate){
                annualInterestRate = newAnnualInterestRate;
        }
       
        public String getDateCreated(){
                return dateCreated.toString();
        }
       
        public double getMonthlyInterestRate(){
                return Math.pow(1.0D+annualInterestRate, 1/12.0D) - 1.0D;
        }
       
        public double withdraw(double a){
                return balance - a;
        }
       
        public double deposit(double a){
                return balance + a;
        }
}

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Thank you in advance!

Your deposit and withdraw methods do not change the value of balance. They merely return balance plus/minus the value passed to the methods

Can you please tell me if this is good? It's working ... And tell me if tere are other alternatives just for my knowledge.a


The new code:

Code:

---

package Chapter8;

import java.util.*;

public class Ex8_7 {
        public static void main (String args[]){
               
                Account account = new Account(1122, 20000.0D);
               
                account.setAnnualInterestRate(4.5D);
               
                account.withdraw(2500.0D);
               
                account.deposit(3000.0D);
               
                System.out.print("The balance is "+account.getBalance()+"\n"+"The monthly interest rate is "+account.getMonthlyInterestRate()+"\n"
                                +"The date when this account was created is: "+account.getDateCreated());
               
        }
}

class Account{
       
        private int id;
        private double balance;
        private double annualInterestRate;
        private Date dateCreated = new Date();
       
        Account(int newID, double newBalance){
                id = newID;
                balance = newBalance;
        }
       
        public int getID(){
                return id;
        }
       
        public void setID(int newID){
                id = newID;
        }
       
        public double getBalance(){
                return balance;
        }
       
        public double setBalance(double newBalance){
                return balance = newBalance;
        }
       
        public double getAnnualInterestRate(){
                return annualInterestRate;
        }
       
        public void setAnnualInterestRate(double newAnnualInterestRate){
                annualInterestRate = newAnnualInterestRate;
        }
       
        public String getDateCreated(){
                return dateCreated.toString();
        }
       
        public double getMonthlyInterestRate(){
                return Math.pow(1.0D+annualInterestRate, 1/12.0D) - 1.0D;
        }
       
        public double withdraw(double a){
                return setBalance(balance-a);
        }
       
        public double deposit(double a){
                return setBalance(balance+a);
        }
}

---

looks good to me....but why is there a setBalance method? makes the code more confusing to me. You also already have a getBalance method to return the balance, so the withdraw/deposit methods have no need to return anything. I would do it like this personally....

Code:

---

private void withdraw(double balance) {
this.balance = balance;
}

---

Quote:

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Originally Posted by Danieldcc

looks good to me....but why is there a setBalance method? makes the code more confusing to me. You also already have a getBalance method to return the balance, so the withdraw/deposit methods have no need to return anything. I would do it like this personally....

Code:

---

private void withdraw(double balance) {
this.balance = balance;
}

---

---

Yes, you're wright, but the "this." concept is explained in the next chapters so I didn't know about it ... I follow the book. Thank you very much! :)

Edit1: Oh, the withdraw and deposit methods must return the "balance - a" so is must be an expression there for the "+/-" operations wright?

true, hung over so not sure what i was thinking

private void withdraw(double amount) {
balance = balance - amount;
}