CODEWITHSUNDEEP
java
jshield
jshield

Reputation: 183

cannot make a static reference to the non-static field

I apologize ahead of time if this code isn't formatted correctly, trying to paste instead of retyping each line. If it isn't right, can someone tell me an easy way to paste multiple lines of code at once?

My main question is that I keep getting an error message stating: Cannot make a static reference to the non-static field balance.

I have tried making the methods static, with no result, and making the main method non-static by removing "static" from the header, but then I get the message: java.lang.NoSuchMethodError: main Exception in thread "main"

Does anyone have any ideas? Any help is appreciated.

public class Account {

    public static void main(String[] args) {
        Account account = new Account(1122, 20000, 4.5);

        account.withdraw(balance, 2500);
        account.deposit(balance, 3000);
        System.out.println("Balance is " + account.getBalance());
        System.out.println("Monthly interest is " + (account.getAnnualInterestRate()/12));
        System.out.println("The account was created " + account.getDateCreated());
    }

    private int id = 0;
    private double balance = 0;
    private double annualInterestRate = 0;
    public java.util.Date dateCreated;

    public Account() {
    }

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

    public void setId(int i) {
        id = i;
    }

    public int getID() {
        return id;
    }

    public void setBalance(double b){
        balance = b;
    }

    public double getBalance() {
        return balance;
    }

    public double getAnnualInterestRate() {
        return annualInterestRate;
    }

    public void setAnnualInterestRate(double interest) {
        annualInterestRate = interest;
    }

    public java.util.Date getDateCreated() {
        return this.dateCreated;
    }

    public void setDateCreated(java.util.Date dateCreated) {
        this.dateCreated = dateCreated;
    }

    public static double withdraw(double balance, double withdrawAmount) {
        double newBalance = balance - withdrawAmount;
        return newBalance;
    }

    public static double deposit(double balance, double depositAmount) {
        double newBalance = balance + depositAmount;
        return newBalance;
    }   
}

Upvotes: 17

Views: 188218

Answers (7)

Naeem Tahir
Naeem Tahir

Reputation: 1

To access instance variables it is a must to create an object, these are not available in the memory, before instantiation.

Therefore, you cannot make static reference to non-static fields(variables) in Java. If you still, try to do so a compile time error is generated saying “non-static variable math cannot be referenced from a static context”.

Upvotes: 0

ratchet freak
ratchet freak

Reputation: 48196

the lines 

account.withdraw(balance, 2500);
account.deposit(balance, 3000);

you might want to make withdraw and deposit non-static and let it modify the balance

public void withdraw(double withdrawAmount) {
    balance = balance - withdrawAmount;
}

public void deposit(double depositAmount) {
    balance = balance + depositAmount;
}

and remove the balance parameter from the call

Upvotes: 7

Vivek Vermani
Vivek Vermani

Reputation: 2004

You are trying to access non static field directly from static method which is not legal in java. balance is a non static field, so either access it using object reference or make it static.

Upvotes: 2

armelbaye
armelbaye

Reputation: 1

you can keep your withdraw and deposit methods static if you want however you'd have to write it like the code below. sb = starting balance and eB = ending balance.

Account account = new Account(1122, 20000, 4.5);

    double sB = Account.withdraw(account.getBalance(), 2500);
    double eB = Account.deposit(sB, 3000);
    System.out.println("Balance is " + eB);
    System.out.println("Monthly interest is " + (account.getAnnualInterestRate()/12));
    account.setDateCreated(new Date());
    System.out.println("The account was created " + account.getDateCreated());

Upvotes: -1

Phil
Phil

Reputation: 3520

Just write:

private static double balance = 0;

and you could also write those like that:

private static int id = 0;
private static double annualInterestRate = 0;
public static java.util.Date dateCreated;

Upvotes: 0

wannik
wannik

Reputation: 12696

main is a static method. It cannot refer to balance, which is an attribute (non-static variable). balance has meaning only when it is referred through an object reference (such as myAccount.balance or yourAccount.balance). But it doesn't have any meaning when it is referred through class (such as Account.balance (whose balance is that?))

I made some changes to your code so that it compiles.

public static void main(String[] args) {
    Account account = new Account(1122, 20000, 4.5);
    account.withdraw(2500);
    account.deposit(3000);

and:

public void withdraw(double withdrawAmount) {
    balance -= withdrawAmount;
}

public void deposit(double depositAmount) {
    balance += depositAmount;
}

Upvotes: 20

bluphoenix
bluphoenix

Reputation: 358

The static calls to withdraw and deposit are your problem. account.withdraw(balance, 2500); This line can't work , since "balance" is an instance variable of Account. The code doesn't make much sense anyway, wouldn't withdraw/deposit be encapsulated inside the Account object itself? so the withdraw should be more like 

public void withdraw(double withdrawAmount)
{
    balance -= withdrawAmount;
}

Of course depending on your problem you could do additional validation here to prevent negative balance etc.

Upvotes: 1

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