Confusion about methods

[jim01]

I am having some confusion about methods. I somewhat understand setter and getter methods. I am confused when it comes to void and how to handle methods that do not return or set a new value.

For example, I am working on the following problem:

The class contains:

1. An int data field named id for the account (default 0).

2. A double data field named balance for the account (default 0.0)

3. A double data field named annualInterestRate that stores the current interest rate (default 0.0)

4. A Date data field named dateCreated that stores the date when the account was created.

5. A no-arg constructor that creates a default account.

6. A constructor that creates an account with the specified id and initial balance.

7. The accessor and mutator methods for id, balance, and annualInterestRate.

8. The accessor method for dateCreated.

9. A method named getMonthlyInterestRate() that returns the monthly interest rate.

10. A method named withdraw() that withdraws a specified amount from the account.

11. A method named deposit() that deposits a specified amount to the account.

Then I have to write a test program but I am not worried about that yet.

So, I'm pretty sure I'm good to go up until I get to number ten, creating a method named withdraw() that withdraws a specified amount from the account. From the wording, it is not a get or set method. It appears to be used to subtract a withdraw amount from the account balance. So this is what I have come up with:

public class Account {
  //declare variables
  private int id = 0;
  private double balance = 0.0;
  private double annualInterestRate = 0.0;
  private java.util.Date dateCreated;
	
  //Construct a default account
  public Account(){
  }
	
  //Construct an account with a specified id and initial balance
  public Account(int newId, double initialBalance){
    id = newId;
    balance = initialBalance;		
  }

  //return id
  public int getId(){
    return id;
  }
	
  //set a new id
  public void setID(int id){
    this.id = id;		
  }
	
  //return balance
  public double getBalance(double balance){
    return balance;
  }
	
  //set new balance
  public void setBalance(double balance){
    this.balance = balance;
  }
	
  //return annualInterestRate
  public double getannualInterestRate(double annualInterestRate){
    return annualInterestRate;
  }
	
  //set a new annualInterestRate 
  public void setAnnualInterestRate(double annualInterestRate){
    this.annualInterestRate = annualInterestRate;
  }
	
  //return dateCreated 
  public java.util.Date getDateCreated(){
    return dateCreated;
  }
	
  //return monthly interest rate
  public double getMonthlyInterestRate(){
    double monthlyInterestRate = annualInterestRate / 12;
    return monthlyInterestRate;
  }
	
  //create a main method to withdraw money from account
  private void double withdraw(double amountToWithdraw){
    double withdraw = balance - amountToWithdraw;		
  }	
}

The problem is that I get the following error message in Eclipse. I have no idea what it meas and have not been able to find any information on it in Eclipse help.

"Syntax error on toke "void", volatile expected."

[JosAH]

  //create a main method to withdraw money from account
  private void double withdraw(double amountToWithdraw){
    double withdraw = balance - amountToWithdraw;		
  }

The problem is that I get the following error message in Eclipse. I have no idea what it meas and have not been able to find any information on it in Eclipse help.

"Syntax error on toke "void", volatile expected."

A method can have only one return type: either void (when it doesn't return anything), or double if it returns a value of type double; you tried to specify both.

kind regards,

Jos

[jim01]

A method can have only one return type: either void (when it doesn't return anything), or double if it returns a value of type double; you tried to specify both.

kind regards,

Jos

I see. Thank you. I am still doing something wrong though because even if I change it to this:

  //create a method to withdraw money from account
  public void double withdraw(){
  }

or this:

  //create a method to withdraw money from account
  public void double withdraw(double withdraw){
  }

I get the same error message. It just doesn't like that void

[JosAH]

I see. Thank you. I am still doing something wrong though because even if I change it to this:

  //create a method to withdraw money from account
  public void double withdraw(){
  }

or this:

  //create a method to withdraw money from account
  public void double withdraw(double withdraw){
  }

I get the same error message. It just doesn't like that void

Now you're doing it again "void double" is two return types, which is wrong; it is either "void" or "double", not both of them.

kind regards,

Jos

[Aero]

Hmm can you declare variables in your class and outside your method?

Anyway that looks weird to me.

But the main thing is a void double, that can't happen. A void returns nothing and a double returns a double, you can't combine those. Also a main method, you probably want to use a main(String[] args) for that?

[jim01]

Now you're doing it again "void double" is two return types, which is wrong; it is either "void" or "double", not both of them.

kind regards,

Jos

Ahh, I get it! (finally). When you said return type I focused on the body of the method instead of the header. Don't ask me why because I do not have a good excuse.

Thank you for your help and patience.