AbstractAccount.java

package com.luxoft.bankapp.model;

// this is an incomplete class. use it as example.
public abstract class AbstractAccount {

    protected float balance;

    public AbstractAccount() {
        balance = 0.0f;
    }

    // balance must be greater than or equal to 0
    public AbstractAccount(float balance) {
        if (balance < 0) {
            throw new IllegalArgumentException("Initial balance must be greater than or equal to 0");
        }
        this.balance = balance;
    }

    public float getBalance() {
        return balance;
    }

    public void deposit(float amount) {
        if (amount <= 0) {
            throw new IllegalArgumentException("Amount must be greater than 0");
        }
        balance += amount;
    }
    
    // other methods
}