How to make sure this variable cannot be initialized with a negative value? [duplicate]

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• Prevent Negative numbers for Age without using client side validation 3 answers

Doing an assignment for my university class with a BankAccount class and a BankAccountClient class. One of the things I need to do is "Add a constructor that the client can use to initialize the name and balance. Make sure the balance cannot be initialized with any negative value." I have added the constructor but I am having problems on making sure the balance cannot be initialized with a negative value.

I've thought about trying an if method inside the constructor but can't think of a way of writing it.

public class BankAccount {
    private String name;
    private double balance;

    public BankAccount() {
        this.name = null;
        this.balance = 0;
    }

    public BankAccount(String name, double balance) {
        this.name = name;
        this.balance = balance;
    }
}

public class BankAccountClient {
    public static void main(String[] args) {
        BankAccount ba = new BankAccount("John", 1000);
    }
}