package java_problems_datastructures;


public class CreditCard {
	// Instance variables:
	private String customer; // name of the customer (e.g., ”John Bowman”)
	private String bank; // name of the bank (e.g., ”California Savings”)
	private String account; // account identifier (e.g., ”5391 0375 9387 5309”)
	private int limit; // credit limit (measured in dollars)
	protected double balance; // current balance (measured in dollars)
// Constructors:

	public CreditCard(String cust, String bk, String acnt, int lim, double initialBal) {
		customer = cust;
		bank = bk;
		account = acnt;
		limit = lim;
		balance = initialBal;
	}

	public CreditCard(String cust, String bk, String acnt, int lim) {
		this(cust, bk, acnt, lim, 0.0); // use a balance of zero as default
	}

	// Accessor methods:
	public String getCustomer() {
		return customer;
	}

	public String getBank() {
		return bank;
	}

	public String getAccount() {
		return account;
	}

	public int getLimit() {
		return limit;
	}

	public double getBalance() {
		return balance;
	}

	// Update methods:
	public boolean charge(double price) { // make a charge
		if (price + balance > limit) // if charge would surpass limit
			return false; // refuse the charge
		// at this point, the charge is successful
		balance += price; // update the balance
		return true; // announce the good news
	}

	// Modified method to reject negative payments
	// below method won't accept the negative payments
	// and throws the IllegalArgumentException
	public void makePayment(double amount) { // make a payment

		if (amount < 0) {
			throw new IllegalArgumentException("Can not pay negative amount :( ");
		} else
			balance -= amount;

	}

	// Utility method to print a card's information
	public static void printSummary(CreditCard card) {
		System.out.println("Customer = " + card.customer);
		System.out.println("Bank = " + card.bank);
		System.out.println("Account = " + card.account);
		System.out.println("Balance = " + card.balance); // implicit cast
		System.out.println("Limit = " + card.limit); // implicit cast
	}

	public static void main(String[] args) {
		CreditCard[] wallet = new CreditCard[3];
		wallet[0] = new CreditCard("John Bowman", "California Savings", "5391 0375 9387 5309", 5000);
		wallet[1] = new CreditCard("John Bowman", "California Federal", "3485 0399 3395 1954", 3500);
		wallet[2] = new CreditCard("John Bowman", "California Finance", "5391 0375 9387 5309", 2500, 300);

		for (int val = 1; val <= 16; val++) {
			wallet[0].charge(3 * val);
			wallet[1].charge(2 * val);
			wallet[2].charge(val);
		}

		for (CreditCard card : wallet) {
			CreditCard.printSummary(card); // calling static method
			if (card.getBalance() > 200.0) {
				// below line cause to throw an IllegalArgumentException as we passing negative amount
				card.makePayment(-200);
				System.out.println("New balance = " + card.getBalance());
			}
		}
	}
}

Output:

Customer = John Bowman
Bank = California Savings
Account = 5391 0375 9387 5309
Balance = 408.0
Limit = 5000
Exception in thread "main" java.lang.IllegalArgumentException: Can not pay negative amount :( 
    at java_problems_datastructures.CreditCard.makePayment(CreditCard.java:61)
    at java_problems_datastructures.CreditCard.main(CreditCard.java:92)

Modified the makePayment() method so it will throw IllegalArgumentException if we attemp to pass negative amount