无法返回变量java

Question

public class Account
{
static int accountNum;
static int nextAccountNum = 112200;
static double balance;


    public static void main(String args[])
    {
        Account checkingAccount = new Account(1500.00);
        Account savingAccount = new Account(1000.00);
        Account moneyMarketAccount = new Account(500.00);

        checkingAccount.getAccountNumber();
        savingAccount.getAccountNumber();
        moneyMarketAccount.getAccountNumber();

    }

    public Account(double bal)
    {
        balance = bal;
        accountNum = nextAccountNum;
        nextAccountNum++;
    }

}

Every time I run it, I don't get any return variables. All I see is the process completed text. Looking for help

Answer 1

You didn't output anything. Use System.out.println to output the account balances, eg

System.out.println(checkingAccount.getAccountNumber());

Also, make your accountNum and your balance variables non- static , or else the balance and account numbers will get overwritten with each new instance.

Answer 2

It's often good practice to separate the main function from an class which will have several instances. Getters and setters methods are used for proper encapsulation of class variables, as an account probably should have. An example is below.

Main.java

public class Main {
    public static void main(String args[])
    {
        Account checkingAccount = new Account(1,1500.00);
        Account savingAccount = new Account(2,1000.00);
        Account moneyMarketAccount = new Account(3,500.00);

        System.out.println("Account " + checkingAccount.getAccountNumber() 
                + " has balance of: " + checkingAccount.getBalance());
        System.out.println("Account " + savingAccount.getAccountNumber() 
                + " has balance of: " + savingAccount.getBalance());
        System.out.println("Account " + moneyMarketAccount.getAccountNumber() 
                + " has balance of: " + moneyMarketAccount.getBalance());
    }
}

Account.java

public class Account
{
private int accountNum;
private int nextAccountNum = 112200;
private double balance;

    public Account(int accountNum, double balance)
    {
        this.balance = balance;
        this.accountNum = accountNum;
    }

    public int getAccountNumber() {
        return accountNum;
    }

    public double getBalance() {
        return balance;
    }

    public void setBalance(int balance) {
        // check if balance variable is a correct value
        // before setting it to the class variable
        this.balance = balance;
    }

}

Answer 3

One problem is that accountNum and balance are declared static . You need them to be instance fields so each instance of Account has its own values.

The reason you get no output is that your main() method creates several Account objects but doesn't do anything with them.

public class Account
{
    static int nextAccountNum = 112200;
    int accountNum;
    double balance;

    public static void main(String args[])
    {
        Account checkingAccount = new Account(1500.00);
        Account savingAccount = new Account(1000.00);
        Account moneyMarketAccount = new Account(500.00);

        checkingAccount.getAccountNumber();
        savingAccount.getAccountNumber();
        moneyMarketAccount.getAccountNumber();

        System.out.println("Checking: " + checkingAccount.toString());    
        System.out.println("Savings: " + savingAccount.toString());    
        System.out.println("Money market: " + moneyMarketAccount.toString());    
    }

    public Account(double bal)
    {
        balance = bal;
        accountNum = nextAccountNum;
        nextAccountNum++;
    }

    @Override
    public String toString() {
        return "Account " + accountNum + ": balance=" + balance;
    }    
}