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Type mismatch: Cannot convert from void to double

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Join Date: Oct 2007

Posts: 25

Reputation: Tyster is an unknown quantity at this point

Solved Threads: 1

Tyster

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Type mismatch: Cannot convert from void to double

Aug 26th, 2008

Hi Folks,

I'm a Java newbie so please forgive me if you've heard this one before...

Got a question for ya about an small app I am working on.

I have a banking app that creates accounts, then makes deposits and withdrawls to/from these accounts. Its very simple. I have a BankAccount class and in that class I have the following deposit method...

//Deposit method.
public void deposit(double dAmount) {

if(dAmount > 0) { // Check that deposit amount is more than zero dollars..
balance = balance + dAmount;} // Update balance with new balance.

else {JOptionPane.showMessageDialog( null, "Error: You must deposit more than 0 dollars.");}

The problem I am having is getting (retrieving) the new balance value in my tester class (with main()). I created the accounts using an ArrayList named 'accounts'. So to get the new balance I do...

//Deposits

for(int j = 0; j < totalAccounts; j++) {

String dep = JOptionPane.showInputDialog("How much would you like to deposit in this account?: ");
double deposit = Double.parseDouble(dep); //Convert string to double
double newBalance = accounts.get(j).deposit(deposit); //Call deposit method

The problem I am seeing is in the last line above. The line says go to index 'j' in the array and get the value after the deposit is made. In Eclipse the error I get is

"Type mismatch: Cannot convert from void to double."

Can anyone offer any suggestions? Should I return the balance in the deposit method instead of merely updating the balance?

I am having the same issue with the withdraw method but I suspect the solution will be the same for each. Any suggestions are greatly appreciated.

Many Thanks!

Tyster

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Join Date: Aug 2008

Posts: 1,158

Reputation: dickersonka will become famous soon enough

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dickersonka dickersonka is offline

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Re: Type mismatch: Cannot convert from void to double

Aug 26th, 2008

Maintain the balance in a private variable inside deposit class.

you are trying to assign a double a value of void here
double newBalance = accounts.get(j).deposit(deposit);

when you withdraw or deposit, have that update a private variable of balance

 Help with Code Tags 
 Java Syntax (Toggle Plain Text) 
private double balance = 0.0;
 
public double getBalance(){
   return balance;
}
public void withdraw(double d){
  //do your processing
 
//now set balance
balance = balance - d;
}
 
 
//in your other ui code call
double newBalance = accounts.get(j).getBalance();
private double balance = 0.0;

public double getBalance(){
   return balance;
}
public void withdraw(double d){
  //do your processing

//now set balance
balance = balance - d;
}


//in your other ui code call
double newBalance = accounts.get(j).getBalance();

Custom Application & Software Development
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Join Date: Oct 2007

Posts: 25

Reputation: Tyster is an unknown quantity at this point

Solved Threads: 1

Tyster

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Re: Type mismatch: Cannot convert from void to double

Aug 26th, 2008

Many Thanks! I'll give that a try.

Tyster

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Originally Posted by dickersonka

Maintain the balance in a private variable inside deposit class.

you are trying to assign a double a value of void here
double newBalance = accounts.get(j).deposit(deposit);

when you withdraw or deposit, have that update a private variable of balance
Help with Code Tags

Java Syntax (Toggle Plain Text)
private double balance = 0.0;
 
public double getBalance(){
   return balance;
}
public void withdraw(double d){
  //do your processing
 
//now set balance
balance = balance - d;
}
 
 
//in your other ui code call
double newBalance = accounts.get(j).getBalance();
private double balance = 0.0; public double getBalance(){ return balance; } public void withdraw(double d){ //do your processing //now set balance balance = balance - d; } //in your other ui code call double newBalance = accounts.get(j).getBalance();